nota ccna exp 2 - routing protocols and concepts

288
NOTA KURSUS CCNA Exploration Module 2 Routing Protocols & Concepts Siri /2010 Nama Peserta : Tarikh : Masa : 8:30 pagi - 5:00 petang Tempat : INTAN NetAcad, Makmal Siber 4, Aras 3 IMATEC, INTAN Bukit Kiara, Kuala Lumpur C C C C N N A A E E X X P P L L O O R R A A T T I I O O N N M M O O D D U U L L 2 2 Anjuran: Program Pembangunan Kepakaran ICT Pusat ICT Institut Tadbiran Awam Negara (INTAN) Jabatan Perkhidmatan Awam Malaysia http://www.intanbk.intan.my

Upload: amirnizan-abd-wahab

Post on 03-Apr-2015

418 views

Category:

Documents


10 download

TRANSCRIPT

Page 1: Nota CCNA Exp 2 - Routing Protocols and Concepts

NOTA KURSUS

CCNA Exploration Module 2 Routing Protocols & Concepts Siri    /2010 

 

Nama Peserta : Tarikh : Masa : 8:30 pagi - 5:00 petang Tempat : INTAN NetAcad, Makmal Siber 4, Aras 3 IMATEC, INTAN Bukit Kiara, Kuala Lumpur

    CC  CC  NN  AA    EE  XX  PP  LL  OO  RR  AA  TT  II  OO  NN    MM  OO  DD  UU  LL    22   Anjuran:

Program Pembangunan Kepakaran ICT Pusat ICT Institut Tadbiran Awam Negara (INTAN) Jabatan Perkhidmatan Awam Malaysia http://www.intanbk.intan.my

Page 2: Nota CCNA Exp 2 - Routing Protocols and Concepts

Introduction to Routing and Packet Forwardingg

Chapter 1: Routing Protocols and Concepts

Modified by Hasimi Sallehudin

1Institut Tadbiran Awam Negara© 2010 Cisco Systems, Inc. All rights reserved.

Objectives

� Identify a router as a computer with an OS andde y a ou e as a co pu e a OS a dhardware designed for the routing process.

� Demonstrate the ability to configure devices andDemonstrate the ability to configure devices andapply addresses.

� Describe the structure of a routing tableDescribe the structure of a routing table.

� Describe how a router determines a path and switches packetsswitches packets

2© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 3: Nota CCNA Exp 2 - Routing Protocols and Concepts

Router as a Computer

� Describe the basic purpose of a routeresc be e bas c pu pose o a ou e-Computers that specialize in sending packets over the data network.They are responsible for interconnecting networks by selecting the best path for a packet to travel and forwarding packets to their destination

� Routers have many of the same hardware and software components that are found in other computersp pincluding:

–CPU–RAM–ROM

3© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

–Operating System

Router as a Computer

� Router components and their functions”p�CPU - Executes operating system instructions

� such as system initialization, routing functions, and switching functions.�Random access memory (RAM) RAM stores the instructions and data needed�Random access memory (RAM) -RAM stores the instructions and data neededto be executed by the CPU. RAM is used to store these components:

–Operating System: The Cisco IOS (Internetwork Operating System) is copied into RAM during bootup.g p–Running Configuration File: This is the configuration file that stores the configuration commands that the router IOS is currently using.–IP Routing Table: This file stores information about directly connected and g yremote networks. It is used to determine the best path to forward the packet.–ARP Cache: This cache contains the IPv4 address to MAC address mappings, similar to the ARP cache on a PC. The ARP cache is used on

h h LAN i f h E h i frouters that have LAN interfaces such as Ethernet interfaces.–Packet Buffer: Packets are temporarily stored in a buffer when received on an interface or before they exit an interface.

4© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

RAM is volatile memory and loses its content when the router is powered down or restarted.

Page 4: Nota CCNA Exp 2 - Routing Protocols and Concepts

Router as a Computer

� Router components and their functions”ou e co po e s a d e u c o s�Read-only memory (ROM) - Holds diagnostic software used when router is powered up. Stores the router’s bootstrap program.p g

–ROM is a form of permanent storage.Cisco devices use ROM to store:

–The bootstrap instructions–Basic diagnostic software–Scaled-down version of IOS–Scaled-down version of IOS

ROM uses firmware, which is software that is embedded inside the integrated circuit.

– Firmware includes the software that does not normally need to be modified or upgraded, such as the bootup instructions. – ROM does not lose its contents when the router loses power

5© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

or is restarted.

R t C tRouter as a Computer� Router components and their functions”

�Non-volatile RAM (NVRAM) - Stores startup configuration. This may include IP addresses (Routing protocol Hostname of router)addresses (Routing protocol, Hostname of router)

�NVRAM (Nonvolatile RAM) does not lose its information when power is turned off. This is in contrast to the most common forms of RAM, such as DRAM, that requires continual power to maintain its information. �NVRAM is used by the Cisco IOS as permanent storage for the startup configuration file�NVRAM is used by the Cisco IOS as permanent storage for the startup configuration file.

�All configuration changes are stored in the running-config file in RAM, and with few exceptions, are implemented immediately by the IOS. �To save those changes in case the router is restarted or loses power, the running-config must be copied to NVRAM where it is stored as the startup-config file NVRAM retains itsmust be copied to NVRAM, where it is stored as the startup-config file. NVRAM retains itscontents even when the router reloads or is powered off.

�Flash memory - Contains the operating system (Cisco IOS)�In most models of Cisco routers, the IOS is permanently stored in flash memory and copied into RAM during the bootup process, where it is then executed by the CPU. �Flash consists of SIMMs or PCMCIA cards, which can be upgraded to increase the amount of flash memoryincrease the amount of flash memory.

�Interfaces - There exist multiple physical interfaces that are used to connect network. Examples of interface types:-Ethernet / fast Ethernet interfaces

6© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

-Serial interfaces-Management interfaces

Page 5: Nota CCNA Exp 2 - Routing Protocols and Concepts

Router as a Computer

� Router componentsou e co po e s

7© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Internetwork Operating System

� The operating system software used in Cisco routers is known as Cisco Internetwork Operating System (IOS)Internetwork Operating System (IOS).

– Cisco IOS is a multitasking operating system that is integrated with routing, switching, internetworking, and telecommunications functions.

� Although the Cisco IOS may appear to be the same on many routers,Although the Cisco IOS may appear to be the same on many routers,there are many different IOS images.

– An IOS image is a file that contains the entire IOS for that router. Cisco creates many different types of IOS images, depending upon the model of the router and the features within the IOS.the router and the features within the IOS.– Typically the more features in the IOS, the larger the IOS image, and therefore, the more flash and RAM that is required to store and load the IOS.

� Although some routers provide a graphical user interface (GUI), the d li i t f (CLI) i h th d fcommand line interface (CLI) is a much more common method of

configuring Cisco routers. – The CLI is used throughout this curriculum.

� Upon bootup the startup config file in NVRAM is copied into RAM and� Upon bootup, the startup-config file in NVRAM is copied into RAM andstored as the running-config file.

– IOS executes the configuration commands in the running-config. Any changes entered by the network administrator are stored in the running-config and are immediately implemented by the IOS

8© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

config and are immediately implemented by the IOS.

Page 6: Nota CCNA Exp 2 - Routing Protocols and Concepts

Overview - Managing Cisco IOS Software (cont)Overview Managing Cisco IOS Software (cont)

9© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Router as a Computer

� Major phases to theajo p ases o erouter boot-up process

�Test router hardwarePower-On Self Test (POST)Execute bootstrap loaderp

�Locate & load Cisco IOS software

Locate IOS-Locate IOS-Load IOS

�Locate & load startup configuration file or enter setup mode

-Bootstrap program looks

10© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

p p gfor configuration file

Page 7: Nota CCNA Exp 2 - Routing Protocols and Concepts

Stages of the router power-on boot sequence

11© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

R t C tRouter as a Computer� Major phases to the router boot-up process

Step 1 and 2: Test router hardwareP O S lf T t (POST)•Power-On Self Test (POST)

–During this self-test, the router executes diagnostics from ROM on several hardware components including the CPU, RAM, and NVRAM

•Execute bootstrap loader–The main task of the bootstrap program is to locate the Cisco IOS and load it into RAM.–Note: At this point, if you have a console connection to the router, you will begin to see output on the screen.

Step 3 and 4: Locate & load Cisco IOS softwareLocate IOS and Load IOS-Locate IOS and Load IOS

–The IOS is typically stored in flash memory, but can also be stored in other places such as a TFTP server.–If a full IOS image can not be located, a g ,scaled-down version of the IOS is copied from ROM into RAM. This version of IOS is used to help diagnose any problems and can be used to load a complete version of the IOS into RAM.

12© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

–Note: A TFTP server is usually used as a backup server for IOS but it can also be used as a central point for storing and loading the IOS.

Page 8: Nota CCNA Exp 2 - Routing Protocols and Concepts

R t C tRouter as a ComputerStep 5 and 6: Locate & load startup configuration file or enter setup

mode

-After the IOS is loaded, the bootstrap program searches for the startup configuration file, known as startup-config, in NVRAM. This parameters including:

•interface addressesinterface addresses•routing information•passwords•any other configurationsy g

–If the startup-config, is located in NVRAM, it is copied into RAM as the running-config.

•The IOS loads the commands in the file, one line at a timetime.

–If the startup configuration file does not exist in NVRAM, the router may search for a TFTP server.

• If the router detects that it has an active link to another configured router, it sends a broadcast searching for a configuration file across the active link. You will eventually see message like the following one:•%Error opening tftp://255.255.255.255/network-confg

13© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

%Error opening tftp://255.255.255.255/network confg(Timed out)•%Error opening tftp://255.255.255.255/cisconet.cfg (Timed out)

Router as a ComputerRouter as a Computer� Locate & load startup configuration file or enter setup

mode–Enter Setup Mode (Optional). If the startup configuration file can not be located the routerconfiguration file can not be located, the routerprompts the user to enter setup mode.

•Setup mode is a series of questions prompting the user for basic configuration information. Setup mode is not intended to be used to enter complex router configurations and it is notcomplex router configurations, and it is notcommonly used by network administrators.

–When booting a router that does not contain a startup configuration file, you will see the following question after the IOS has been loaded:

•Would you like to enter the initial configuration dialog? [yes/no]: no

–Setup mode will not be used in this course to configure the router. When prompted to enter setup mode, always answer no. If youe te setup ode, a ays a s e o youanswer yes and enter setup mode, you can press Ctrl-C at any time to terminate the setup process.

–When setup mode is not used, the IOS creates a default running-config.default running config.

•The default running-config is a basic configuration file that includes the router interfaces, management interfaces, and certain default information. Th d f lt i fi d t t i

14© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

•The default running-config does not contain any interface addresses, routing information, passwords, or other specific configuration information.

Page 9: Nota CCNA Exp 2 - Routing Protocols and Concepts

Router as a Computer

� Verify the router boot-up process:

show version

-The show version command is used to view information about the router during the bootup process.Information includes:Information includes:

�Image name & IOS versionIOS (tm) C2600 Software (C2600 I M) V i 12 2(28)(C2600-I-M), Version 12.2(28),RELEASE SOFTWARE (fc5).

�Bootstrap version stored in ROMO S�ROM: System Bootstrap,

Version 12.1(3r)T2, RELEASE SOFTWARE (fc1)

�Image file name & where it was�Image file name & where it wasloaded from

�System image file is "flash:c2600-i-mz 122-28 bin"

15© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

flash:c2600 i mz.122 28.bin

Router as a Computer

� Verify the router boot-up process:show version

�Platform model number �CPU�Amount of RAM�Amount of RAM

�Some series of routers, like the 2600, use a fraction of DRAM as packet memory. Packet memory is

d f b ff i k tused for buffering packets.�To determine the total amount of DRAM on the router, add both numbers. In this example, the Cisconumbers. In this example, the Cisco2621 router has 60,416 KB (kilobytes) of free DRAM used for temporarily storing the Cisco IOS and other system processes. The y pother 5,120 KB is dedicated for packet memory. The sum of these numbers is 65,536K, or 64 megabytes (MB) of total DRAM.

16© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 10: Nota CCNA Exp 2 - Routing Protocols and Concepts

Router as a Computer

� Verify the router boot-up process:show version

�Number & type of interfaces2 FastEthernet/IEEE 802.3 interface(s)2 Low-speed serial(sync/async) network interface(s)

�Amount of NVRAM�32K bytes of non-volatile configuration memory.�NVRAM is used to store the startup config filestartup-config file.

�Amount of flash�16384K bytes of processor board System flash (Read/Write)System flash (Read/Write)�This is the amount of flash memory on the router. Flash is used to permanently store the Cisco IOS.

17© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Router as a Computer

� Configuration register

show version

� Configuration register is 0x2102–The last line of the show version command displays the current

fi d l f th ftconfigured value of the softwareconfiguration register in hexadecimal. If there is a second value displayed in parentheses, it denotes the configuration registerdenotes the configuration registervalue that will be used during the next reload.–The configuration register has

l i l di dg g

several uses, including passwordrecovery. The factory default setting for the configuration register is 0x2102. This value indicates that th t ill tt t t l dthe router will attempt to load a Cisco IOS software image from flash memory and load the startup configuration file from NVRAM.

18© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

–Note: The configuration register is discussed in more detail in a later course.

Page 11: Nota CCNA Exp 2 - Routing Protocols and Concepts

C fi ti i tConfiguration register� The order in which the router looks for system

bootstrap depends on the boot field setting in the configuration register.g g

The default configuration register setting can be changed with the global configuration mode command config-register.Use a hexadecimal number as the argument for this command.command.

� The configuration register is a 16-bit register in NVRAM.

The lowest four bits of the configuration register form the boot field. To ensure that the upper 12 bits are not changed, first retrieve the current values of the configuration register using the show version command. Then use the config-register command, changing only the value of the last hexadecimal digit.

19© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Configuration register (cont )Configuration register (cont.)� To enter the ROM monitor mode, set the configuration

register value to 0xnnn0,where nnn represents the previous value of the non-boot field di itdigits.This value sets the boot field bits to 0000 binary. From ROM monitor, boot the operating system manually by using the b command at the ROM monitor prompt.

� To configure the system to boot automatically from ROM� To configure the system to boot automatically from ROM,set the configuration register to 0xnnn1,

This value sets the boot field bits to 0001 binary.

� To configure the system to use the boot system commands in NVRAM set the configuration register tocommands in NVRAM, set the configuration register toany value from 0xnnn2 to 0xnnnF,

These values set the boot field bits to a value between 0010 and 1111 binary. Using boot system commands in NVRAM is the default.

Check Configuration Register value (NVRAM)

0 = ROM Monitor mode

1 = ROM IOS

20© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

1 ROM IOS

2 - 15 = Boot system from Flash

Page 12: Nota CCNA Exp 2 - Routing Protocols and Concepts

How a Cisco device locates and loads IOS The config-register can be Downloaded from:http:// lilligren com/cisco/do nloads htm� Demo

config-register

http://www.lilligren.com/cisco/downloads.htm

21© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Configuration register: 0, 1, and 2 and above

22© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 13: Nota CCNA Exp 2 - Routing Protocols and Concepts

Configuration register: 2102 and 2142Configuration register: 2102 and 2142

23© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Configuration registerConfiguration registerRouter(config)#config-register value1 2

3

24© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 14: Nota CCNA Exp 2 - Routing Protocols and Concepts

Stages of the router power-on boot sequenceStages of the router power-on boot sequence1. ROM

1. POST

2. Bootstrap code executed

1, 2

3. Check Configuration Register value (NVRAM)

0 = ROM Monitor mode

1 = ROM IOS

2 - 15 = Boot system from flash

3

42. Check for IOS boot system commands in startup-config file (NVRAM)

If boot system commands in startup-config

a. Run boot system commands in order they appear in startup-config to locate the IOS

4

b If boot system commands fail, use default fallback sequence to locate the IOS (Flash, TFTP, ROM)

3. Locate and load IOS, Default fallback sequence: No IOS boot system commands in startup-config

a. Flash (sequential)

b. TFTP server (netboot) - The router uses the configuration register value to form a filename from which to boot a default system image stored on a network server.

c. ROM (partial IOS) or keep retrying TFTP depending upon router model

- If no IOS located, get partial IOS version from ROM

4. Locate and load startup-configa. If startup-config found, copy to running-config

b. If startup-config not found, prompt for setup-mode

c If setup mode bypassed create a “skeleton” default running config (no startup config)

25© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

c. If setup-mode bypassed, create a skeleton default running-config (no startup-config)

How a Cisco device locates and loads IOSHow a Cisco device locates and loads IOS� The router can use its own fallback

sequence to load the software. qThe router looks to the boot system commands saved in NVRAM.(Tony) The router has its own default fallback sequence This default sequencefallback sequence. This default sequencecan be interrupted by using the boot system command and/or config register.

� The settings in the configuration registerg g genable the following alternatives:

Global configuration mode boot system commands can be specified to enter fallback sources.fallback sources.If NVRAM lacks boot system commandsthe system by default uses the Cisco IOS software in flash memory.

(T ) N b t t d(Tony) No boot system commands(Tony) IOS specified in the boot system does not exist

If flash memory is empty, the router then

26© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

If flash memory is empty, the router thenattempts to use TFTP to load an IOS image from the network.

Page 15: Nota CCNA Exp 2 - Routing Protocols and Concepts

How a Cisco device locates and loads IOS

27© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

U i th b t t dUsing the boot system command� The three examples show boot system

entries which specify that a Cisco IOS ft i ill l dsoftware image will loadFirst from flash memory,

Flash memory – A system image from flash memory can be loadedflash memory can be loaded.

Then from a network server, andNetwork server – In case flash memory becomes corrupted, a system i b l d d f TFTPimage can be loaded from a TFTPserver.

Finally from ROM: ROM – If flash memory is corruptedROM If flash memory is corruptedand the network server fails to load the image, booting from ROM is the final bootstrap option in software. However the system image in ROM isHowever, the system image in ROM isa subset of the Cisco IOS that lacks the protocols, features of the full Cisco IOS.Also, if the software has been updated, the router may have an older version

28© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

the router may have an older versionstored in ROM.•The command copy running-config startup-config saves the commands in NVRAM.

Page 16: Nota CCNA Exp 2 - Routing Protocols and Concepts

How a Cisco device locates and loads IOS

• What happen when both config-register and boot• What happen when both config-register and bootsystem both exist in the startup-config?

• Which one has the priority?p y

29© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Management Ports

� Routers have physical connectors that are d t th t Th tused to manage the router. These connectors

are known as management ports. –Unlike Ethernet and serial interfaces, management ports are not used for packet f diforwarding.

� The most common management port is the console port.

The console port is used to connect a terminal–The console port is used to connect a terminal,or most often a PC running terminal emulator software, to configure the router without the need for network access to that router. –The console port must be used during initialThe console port must be used during initialconfiguration of the router.

� Another management port is the auxiliary port. –Not all routers have auxiliary ports.y p–At times the auxiliary port can be used in ways similar to a console port. It can also be used to attach a modem. –Auxiliary ports will not be used in this

30© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Auxiliary ports will not be used in thiscurriculum.

Page 17: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routers determine the best path

� Router Interface is a physical connector that enables a router to send or receive packets

–Each interface connects to a separate network•different IP network•different IP network

� Typically, the interfaces connect to various types of networks, which means that different yptypes of media and connectors are required. Types of router interfaces:

-EthernetEthernet-Fastethernet-Serial-DSL-ISDNCable

31© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

-Cable

Two major groups of Router Interfaces: LAN & WAN� LAN Interfaces: such as Ethernet and

FastEthernet�Are used to connect router to LAN network�Has a layer 2 MAC address

�a router Ethernet interface participates in the ARP process for that LAN.

�Can be assigned a Layer 3 IP address�Can be assigned a Layer 3 IP address�Usually consist of an RJ-45 jack

�When a router is connected to a switch a straight-through cable isswitch, a straight through cable isused.�When two routers are connected directly through the Ethernet interfaces or when a PC NIC isinterfaces, or when a PC NIC isconnected directly to a router Ethernet interface, a crossovercable is used.

32© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 18: Nota CCNA Exp 2 - Routing Protocols and Concepts

f f &Two major groups of Router Interfaces: LAN & WAN� WAN Interfaces- such as serial, ISDN, and

F R lFrame Relay�Are used to connect routers to external networks that interconnect LANs, usually over a larger geographical distance..�Depending on the WAN technology, a p g gy,layer 2 address may be used.�Uses a layer 3 IP address

�Similar to LAN interfaces each WAN�Similar to LAN interfaces, each WANinterface has its own IP address and subnet mask, which identifies it as a member of a specific network.

�The Layer 2 encapsulation can be of different types,

�PPP, Frame Relay, and HDLC (High-

33© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

, y, ( gLevel Data Link Control).

f f &Two major groups of Router Interfaces: LAN & WAN� The router in the figure has four

i t finterfaces.–Each interface has a Layer 3 IP address and subnet mask that configures it for a different network. –The Ethernet interfaces also have Layer 2 Ethernet MAC addresses.

� The WAN interfaces are using different Layer 2 encapsulations.

S 0/0/0 C–Serial 0/0/0 is using HDLC–Serial 0/0/1 is using PPP. –Both of these serial point-to-pointBoth of these serial point to pointprotocols use a broadcast address for the Layer 2 destination address when encapsulating the IP packet into a data link

34© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

frame.

Page 19: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routers determine the best path

� A router connects multiple networks. p�This means that it has multiple interfaces that each belong to a different IP network. �When a router receives an IP packet on one interface it�When a router receives an IP packet on one interface, itdetermines which interface to use to forward the packet onto its destination.The interface that the ro ter ses to for ard the packet ma be�The interface that the router uses to forward the packet may be

the network of the final destination of the packet (the network with the destination IP address of this packet), or it may be a network connected to another router that is used to reach the destinationconnected to another router that is used to reach the destinationnetwork.

� Routers are the network center-Routers generally have 2 connections:

-WAN connection (Connection to ISP)

35© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

-LAN connection

Routers determine the best path

� Routers examine a packet’s destination IP address andou e s e a e a pac e s des a o add ess a ddetermine the best path by enlisting the aid of a routing table

36© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 20: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routers determine the best path

� The primary responsibility of a router is to direct packets destined for local and remote networks by:and remote networks by:

–Determining the best path to send packets –Forwarding packets toward their destination

� The router uses its routing table to determine the best path to forward the� The router uses its routing table to determine the best path to forward thepacket.

–When the router receives a packet, it examines its destination IP address and searches for the best match with a network address in the router's routing table. –The routing table also includes the interface to be used to forward the packet. Once a match is found, the router encapsulates the IP packet into the data link frame of the outgoing or exit interface, and the packet is then forwarded toward its destination.

� It is very likely that a router will receive a packet that is encapsulated in one type of data link frame, such as an Ethernet frame and when forwarding the packet, the router will encapsulate it in a different type of data link

37© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routers determine the best path

� Routers Operate at Layers 1, 2 & 3ou e s Ope a e a aye s , & 3–A router makes its primary forwarding decision at Layer 3, but as we saw earlier, it participates in Layer 1 and Layer 2participates in Layer 1 and Layer 2processes as well. �Router receives a stream of encoded bits�Bits are decoded and passed to layer 2�Router de-encapsulates the frame�Remaining packet passed up to layer 3

-Routing decision made at this layer by examining destination IP addressexamining destination IP address

�Packet is then re-encapsulated & sent out outbound interface

38© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 21: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routers determine the best path

� PC1 operates at all seven layers, encapsulating the data and sending the frame out as a stream of encoded bits to R1 its default gatewayof encoded bits to R1, its default gateway.

� R1 receives the stream of encoded bits on its interface. The bits are decoded and passed up to Layer 2, where R1 decapsulates the frame. The router examines the destination address of the data link frame to determine if it matches the receiving interface, including a broadcast or multicast address. If there is a match with the data portion of the frame, the IP packet is passed up to Layer 3, where R1 makes its routing decision. R1 then re-encapsulates the packet into a new Layer 2 data link frame and forwards it out the outbound interface as a stream of encoded bits.

� R2 receives the stream of bits, and the process repeats itself. R2 decapsulates the frame and passes the data portion of the frame, the IP packet, to Layer 3 where R2 makes its routing decision. R2 then re-encapsulates the packet into a new Layer 2 data link frame and forwards it out the outbound interface as a stream of encoded bits.

� This process is repeated once again by router R3, which forwards the IP packet, encapsulated inside a data link frame and encoded as bits, to PC2.

39© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Configure Devices and Apply Addresses

� Implementing Basic Addressing Schemesp e e g as c dd ess g Sc e es

� When designing a new network or mapping an existing network you must provide the following information innetwork you must provide the following information inthe form of a document:

-Topology drawing that Illustrates physical connectivityp gy g p y y–Address table that provides the following information:

�Device name�Interfaces used�IP addresses�Default gateway

40© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 22: Nota CCNA Exp 2 - Routing Protocols and Concepts

Configure Devices and Apply Addresses

41© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Configure Devices and Apply Addresses

� Basic Router Configuration� A basic router configuration should contain the following:

-Router name - Host name should be uniqueBanner At a minimum banner should warn against unauthorized use-Banner - At a minimum, banner should warn against unauthorized use

-Passwords - Use strong passwords-Interface configurations –

•Specify interface type, •IP address and subnet mask.•Describe purpose of interface. •Issue no shutdown command. •If DCE serial interface issue clock rate command.

� After entering in the basic configuration the following tasks should beAfter entering in the basic configuration the following tasks should becompleted

-Verify basic configuration and router operations.-Save the changes on a router

42© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

-Save the changes on a router

Page 23: Nota CCNA Exp 2 - Routing Protocols and Concepts

Configure Devices and Apply Addresses

brief review from CCNA1Router>Router>enableRouter#Router#config t Router(config)#enable secret classRouter(config)#enable password ciscoRouter(config)#hostname R1R1(config)#R1( fi )#li l 0R1(config)#line console 0R1(config-line)#password ciscoR1(config-line)#loginR1(config-line)#exitR1(config-line)#exitR1(config)#line vty 0 4R1(config-line)#password ciscoR1(config-line)#login

43© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

( g ) gR1(config-line)#exit

Configure Devices and Apply Addresses

brief review from CCNA1Configuring a Banner

From the global configuration mode, configure the

brief review from CCNA1

message-of-the-day (motd) banner. A delimiting character, such as a "#" is used at the beginning and at the end of the message. The delimiter allows you to configure a multiline banner, as shown here.

R1(config)#banner motd #

Enter TEXT message. End with the character '#'.

******************************************

WARNING!! Unauthorized Access Prohibited!!

******************************************

#

Configuring an appropriate banner is part of a good security plan. At a very minimum, a banner should warn against unauthorized access. Never configure a

44© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

banner that "welcomes" an unauthorized user.

Page 24: Nota CCNA Exp 2 - Routing Protocols and Concepts

Limiting Device Access Enable and Enable Secret PasswordsLimiting Device Access – Enable and Enable Secret Passwords� To provide additional security, use enable password

or enable secret command to establish h i i b f i i il d EXECauthentication before accessing privileged EXEC

(enable) mode. Always use the enable secret command, not the older

bl d d if iblenable password command, if possible.

� The following commands are used to set the passwords:

Router(config)#enable password passwordRouter(config)#enable secret password

� If no enable password or enable secret password is� If no enable password or enable secret password isset, the IOS prevents privileged EXEC access from a Telnet session.

Without an enable password having been set a TelnetWithout an enable password having been set, a Telnetsession would appear this way:

Switch>enable% No password set

45© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

% No password setSwitch>

Limiting Device Access Enable and Enable Secret PasswordsLimiting Device Access – Enable and Enable Secret Passwords� Example of enable password and enable secret:

46© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 25: Nota CCNA Exp 2 - Routing Protocols and Concepts

Limiting Device Access – VTY PasswordLimiting Device Access VTY Password� The vty lines allow access to a router via Telnet.

By default, many Cisco devices support 5 VTY lines that are b d 0 t 4numbered 0 to 4.

A password needs to be set for all available vty lines. The same password can be set for all connections. However it is often desirable that a unique password be set forHowever, it is often desirable that a unique password be set forone line to provide a fall-back for administrative entry to the device if the other connections are in use.

� The following commands are used to set a password:g pRouter(config)#line vty 0 4Router(config-line)#password passwordRouter(config-line)#login

� By default, the IOS includes the login command on the VTY lines. This prevents Telnet access to the device without first requiring authentication.

If, by mistake, the no login command is set, which removes the requirement for authentication, unauthorized persons could connect to the line using Telnet. This would be a major security risk.

47© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Encrypting Password DisplayEncrypting Password Display� Another useful command prevents passwords from

showing up as plain text when viewing the fi i filconfiguration files.This is the service password-encryption command.This command causes the encryption of passwords to occur when a password is configured.

� The service password-encryption command applies weak encryption to all unencrypted passwords.yp yp p

This encryption does not apply to passwords as they are sent over media only in the configuration. The purpose of this command is to keep unauthorized p p pindividuals from viewing passwords in the configuration file.

� Once the encryption has been applied, removing the yp pp , gencryption service does not reverse the encryption.

48© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 26: Nota CCNA Exp 2 - Routing Protocols and Concepts

Configuring router passwords (cont )Configuring router passwords (cont.)

WARNING� service password-encryption uses a Cisco Level 7 encryption which is very

easy to decrypt.

� For the GetPass! software www.boson.com

� However, the enable secret <password> uses a stronger encryption method and cannot be easily hacked.

49© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

and !

Configuring router passwords (cont.)g g ( )

Doesn’t work for enable secret!

50© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 27: Nota CCNA Exp 2 - Routing Protocols and Concepts

Configure Devices and Apply Addresses

R1(config)#interface Serial0/0/0R1(config)#interface Serial0/0/0R1(config-if)#ip address 192.168.2.1 255.255.255.0R1(config-if)#description Ciruit#VBN32696-123 (help desk:1-800-555-1234)R1(config-if)#no shutdownR1(config-if)#clock rate 64000

Note: When cabling a point-to-point serial link in our lab environment, one end ofNote: When cabling a point to point serial link in our lab environment, one end ofthe cable is marked DTE and the other end is marked DCE. The router that has the DCE end of the cable connected to its serial interface will need the additional clock rate command configured on that serial interface.This step is only necessary in a lab environmentThis step is only necessary in a lab environment

51© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Configure Devices and Apply Addresses

th F tEth t i t f d t b fi d� the FastEthernet interface needs to be configuredR1(config)#interface FastEthernet0/0R1( fi if)#i dd 192 168 1 1 255 255 255 0R1(config-if)#ip address 192.168.1.1 255.255.255.0R1(config-if)#description R1 LANR1(config if)#no shutdownR1(config-if)#no shutdown

52© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 28: Nota CCNA Exp 2 - Routing Protocols and Concepts

Configure Devices and Apply Addresses

� Each interface must belong to a different network. Alth h th IOS ll t fi IP dd–Although the IOS allows you to configure an IP address

from the same network on two different interfaces, the router will not activate the second interface. –For example, what if you attempt to configure the FastEthernet 0/1 interface on R1 with an IP address on the 192 168 1 0/24 t k? F tEth t 0/0 h l d b192.168.1.0/24 network? FastEthernet 0/0 has already beenassigned an address on that same network. you will get the following message:

R1(config)#interface FastEthernet0/1R1(config-if)#ip address 192 168 1 2 255 255 255 0R1(config-if)#ip address 192.168.1.2 255.255.255.0192.168.1.0 overlaps with FastEthernet0/0

–If there is an attempt to enable the interface with the no shutdown command, the following message will appear:

R1(config-if)#no shutdownR1(config-if)#no shutdown192.168.1.0 overlaps with FastEthernet0/0FastEthernet0/1: incorrect IP address assignment

� The output from the show ip interface brief command shows that the second interface configured for the 192.168.1.0/24 network, FastEthernet 0/1, is still down.

� R1#show ip interface brief

53© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

� R1#show ip interface brief<output omitted>FastEthernet0/1 192.168.1.2 YES manual administratively down down

Configure Devices and Apply Addresses

� Verify Basic Router Configuratione y as c ou e Co gu a o-Issue the show running-config command

•displays the current running configuration that is stored in RAM.

-Issuing the copy running-config startup-config command•Save the basic router configuration

-Additional commands that will enable you to further verify router configuration are:

�Show startup-config - Displays configuration file NVRAMShow startup config Displays configuration file NVRAM�Show IP route - Displays routing table�Show interfaces - Displays all interface configurationsp y g�Show IP int brief - Displays abbreviated interface configuration information

54© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 29: Nota CCNA Exp 2 - Routing Protocols and Concepts

Configure Devices and Apply Addresses

55© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Configure Devices and Apply Addresses

56© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 30: Nota CCNA Exp 2 - Routing Protocols and Concepts

SRouting Table Structure� The primary function of a router is to forward a packet toward its

destination network which is the destination IP address of the packetdestination network, which is the destination IP address of the packet.–To do this, a router needs to search the routing information stored in its routing table.

� Routing Table is stored in ram and contains information:Routing Table is stored in ram and contains information:�Directly connected networks - this occurs when a device is connected to another router interfaceR t l t d t k thi i t k th t i t di tl�Remotely connected networks - this is a network that is not directly

connected to a particular router�network/next hop associations - about the networks include source of i f ti t k dd & b t k d I dd f t hinformation, network address & subnet mask, and Ip address of next-hoprouter

� Show ip route command is used to view a routing tablep g

57© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing Table Structure� The network/exit-interface association can also represent the destination network

address of the IP packet. This association occurs on the router's directly connected networks.

� A directly connected network is a network that is directly attached to one of the router interfaces.

When a router interface is configured with an IP address and subnet mask, the interfaceWhen a router interface is configured with an IP address and subnet mask, the interfacebecomes a host on that attached network. The network address and subnet mask of the interface, along with the interface type and number, are entered into the routing table as a directly connected network. When a router forwards a packet to a host, such as a web server, that host is on the same network as a router's directly connected network.

� A remote network is a network that is not directly connected to the router� A remote network is a network that is not directly connected to the router.In other words, a remote network is a network that can only be reached by sending the packet to another router. Remote networks are added to the routing table using either a dynamic routing protocol or by configuring static routes. Dynamic routes are routes to remote networks that were learned automatically by the router, using a dynamic routing

t l St ti t t t t k th t t k d i i t t llprotocol. Static routes are routes to networks that a network administrator manuallyconfigured.

58© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 31: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table Structure

� As shown in the figure the routing table is displayed with the show ip route d At thi i t th h t b t ti t fi dcommand. At this point, there have not been any static routes configured

nor any dynamic routing protocol enabled. Therefore, the routing table for R1 only shows the router's directly connected networks. For each network listed in the routing table, the following information is included:g , g

–C - The information in this column denotes the source of the route information, directly connected network, static route or a dynamic routing protocol. The C represents a directly connected route.192 168 1 0/24 Thi i th t k dd d b t k f th di tl–192.168.1.0/24 - This is the network address and subnet mask of the directly

connected or remote network. In this example, both entries in the routing table, 192.168.1./24 and 192.168.2.0/24, are directly connected networks.–FastEthernet 0/0 - The information at the end of the route entry represents the y pexit interface and/or the IP address of the next-hop router. In this example, both FastEthernet 0/0 and Serial0/0/0 are the exit interfaces used to reach these networks.

59© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing Table Structure

� PCs also have a routing table.Cs a so a e a ou g ab eIn the figure, you can see the route print command output. The command reveals the configured or acquired default gateway, connected loopback multicast and broadcast networksconnected, loopback, multicast, and broadcast networks.The output from route print command will not be analyzed during this course. It is shown here to emphasize the point that g p pall IP configured devices should have a routing table.

60© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 32: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table Structure

� The following analogies may help clarify the concept of connected static andthe concept of connected, static, anddynamic routes:

� Directly Connected Routes - To visit a neighbor, you only have to go down the

hi h l d li Thig y y g

street on which you already live. Thispath is similar to a directly-connected route because the "destination" is available directly through your " t d i t f " th t t"connected interface," the street.

� Static Routes - A train uses the same railroad tracks every time for a specified route This path is similar to a staticroute. This path is similar to a staticroute because the path to the destination is always the same.

� Dynamic Routes - When driving a car, "d i ll " hyou can "dynamically" choose a

different path based on traffic, weather, or other conditions. This path is similar to a dynamic route because you can choose a new path at many different

61© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

choose a new path at many differentpoints on your way to the destination.

Routing Table StructureRouting Table Structure� Adding a connected network to the routing table

-Router interfaces�Each router interface is a member of a different network�Activated using the no shutdown command�In order for static and dynamic routes to exist in routingIn order for static and dynamic routes to exist in routingtable you must have directly connected networks

62© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 33: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table Structure

� Remote networks are added to the routing table either by configuring static routes or enabling a dynamic routing protocol.g p

� Static routes in the routing table-Includes: network address and subnet mask and IP address of next hop router or exit interface-Denoted with the code S in the routing table-Routing tables must contain directly connected networks used to connect remote networks before static or dynamic routing can be used

63© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing Table Structure

� When to use static routes-When network only consists of a few routers

•Using a dynamic routing protocol in such a case does not present any substantialcase does not present any substantialbenefit.

-Network is connected to internet only through one ISP

There is no need to use a dynamic routing• There is no need to use a dynamic routingprotocol across this link because the ISP represents the only exit point to the Internet.

-Hub & spoke topology is used on a large networknetwork

•A hub-and-spoke topology consists of a central location (the hub) and multiple branch locations (spokes), with each spoke having only one connection to the hubonly one connection to the hub.•Using dynamic routing would be unnecessary because each branch has only one path to a given destination-through the central location

64© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

central location.

Page 34: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table Structure

� Dynamic routing protocols-Are used to add remote networks to a routing table-Are used to discover networks-Are used to update and maintain routing tables

� Automatic network discovery–-Network discovery is the ability of a routing protocol to share information about the networks that it knows about with other routers that are also using the same routing protocol. –Instead of configuring static routes to remote networks on every router, a dynamic routing protocol allows the routers to automatically learn about these networks from other routers.–These networks - and the best path to each network - are added to the router's prouting table and denoted as a network learned by a specific dynamic routing protocol.

� Maintaining routing tablesDynamic routing protocols are used to share routing information with other router & to-Dynamic routing protocols are used to share routing information with other router & to

maintain and up date their own routing table.–Dynamic routing protocols not only make a best path determination to various networks, they will also determine a new best path if the initial path becomes unusable (or if the topology changes)

65© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing Table Structure

•R1 has learned about two remote•R1 has learned about two remotenetworks:

•A route that dynamically used RIP •In the figure R1 has automatically•In the figure, R1 has automaticallylearned about the 192.168.4.0/24 network from R2 through the dynamic routing protocol, RIP (Routingg p , ( gInformation Protocol).

•A static route that was configured manually.

•This is an example of how routing tables can contain routes learned dynamically and configureddynamically and configuredstatically and is not necessarily representative of the best

fi ti f thi t k

66© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

configuration for this network.

Page 35: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table Structure

� IP routing protocols. Example of routing protocols include:g p p g p–RIP (Routing Information Protocol) - - CCNA–IGRP (Interior Gateway Routing Protocol) - - ignore it–EIGRP (Enhanced Interior Gateway Routing Protocol) - - CCNA & NP–OSPF (Open Shortest Path First) - - CCNA & CCNP–IS-IS (Intermediate System-to-Intermediate System) - - CCNP–BGP (Border Gateway Protocol) - - CCNP

RIP (versions 1 and 2), EIGRP, and OSPF are discussed in this course. EIGRP d OSPF l l i d i d t il i CCNP l ith IS IS d BGPand OSPF are also explained in more detail in CCNP, along with IS-IS and BGP.

IGRP is a legacy routing protocol and has been replaced by EIGRP. Both IGRP and EIGRP are Cisco proprietary routing protocols, whereas all other routing protocols listed are standard, non-proprietary protocols.

67© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

protocols listed are standard, non proprietary protocols.

Routing Table Structure� Routing Table Principles

-3 principles regarding routing tables: �Every router makes its decisions alone, based on the information it has in its routing tableinformation it has in its routing table.�Different routing table may contain different information� A routing table can tell how to get to a destination but not g ghow to get back (Asymmetric Routing)

�Routing information about a path from one network to another does not provide routing information about the reverse ordoes not provide routing information about the reverse, orreturn, path.

68© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 36: Nota CCNA Exp 2 - Routing Protocols and Concepts

Router Paths and Packet Switching

� Internet Protocol (IP) packet format contains fields thate e o oco ( ) pac e o a co a s e ds aprovide information about the packet and the sending and receiving hosts

� Fields that are importance for CCNA students:-Version

L 3-IP header length-TTL

Layer 3

-Precedence & type of service-Packet lengthS-Source IP address

-Destination IP address

69© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

� The Layer 2 data link frame usually contains header information with a data link source and destination address, trailer information, and the actual transmitted d t

Router Paths and Packet Switchingdata.

–The data link source address is the Layer 2 address of the interface that sent the data link frame.

� MAC Layer Frame FormatA k t i f d d f t t t th L 3 d d ti ti IPAs a packet is forwarded from router to router, the Layer 3 source and destination IPaddresses will not change; however, the Layer 2 source and destination data link addresses will change.

� MAC Frames are also divided into fields. They include:y-Preamble

•Seven bytes of alternating 1s and 0s, used to synchronize signals

-Start of frame delimiter1 b t i li th b i i f th f

Layer 2

•1 byte signaling the beginning of the frame

-Destination MAC address•6 byte

-Source MAC address•6 byte

-Type/length•2 byte

-Data and pad

70© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Data and pad•46 to 1500 bytes of data; zeros used to pad any data packet less than 46 bytes

-Frame check sequence•4 byte

Page 37: Nota CCNA Exp 2 - Routing Protocols and Concepts

Ethernet frame fields (cont.) � The original Ethernet standards defined the

i i f i 64 b t d thminimum frame size as 64-bytes and themaximum as 1518-bytes.

These numbers include all bytes from the Destination MAC Address field through the 10101011

A Start Frame Delimiterg

Frame Check Sequence field. The Preamble and Start Frame Delimiter fields are not included when quoting the size of a frame. z

10101011.

frame. z

� The IEEE 802.3ac standard released in 1998 extended the maximum allowable frame size to 1522-bytes to allow a "VLAN tag" to be i t d i t th Eth t f f tinserted into the Ethernet frame format.

71© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

http://www.techfest.com/networking/lan/ethernet2.htm

• Peer to Peer Communication is really communication between the headers at each layer. Layers 2 and 3 are best effort or connectionless

72© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

• Layers 2 and 3 are best effort or connectionless.• Layer 4 Transport is connection oriented. The ‘connection’ is in the header.

Page 38: Nota CCNA Exp 2 - Routing Protocols and Concepts

73© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Router Paths: Best Path� Whenever multiple paths to reach the same network

exist, each path uses a different exit interface on the router to reach that network.

– The best path is selected by a routing protocol based on the value or metric it uses to determine the distance to reach a networkto reach a network.

•Metrics can be based on either a single characteristic or several characteristics of a path. •Some routing protocols can base route selection g pon multiple metrics, combining them into a single metric.•The smaller the value of the metric, the better the pathpath.

–Routing protocols, such as RIP, use simple hop-count, which the number of routers between a router and the destination network.

• For example, a router will prefer a path that is 5 hops away over a path that is 10 hops away.

–Other routing protocols, such as OSPF, determine the shortest path by examining the bandwidth of the

74© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

the shortest path by examining the bandwidth of thelinks, and using the links with the fastest bandwidth from a router to the destination network.

Page 39: Nota CCNA Exp 2 - Routing Protocols and Concepts

Router Paths and Packet Switching

� A Metric is a numerical value used by routing protocols help determine the best path to a destinationbest path to a destination

–The smaller the metric value the better the path� 2 types of metrics used by routing protocols are:

Hop count this is the number of routers a packet must travel through to-Hop count - this is the number of routers a packet must travel through toget to its destination

• Hop count of four indicates that a packet must pass through four routers to reach its destination. • If multiple paths are available to a destination, the routing protocol, such as RIP, picks the path with the least number of hops.

-Bandwidth - this is the “speed” of a link also known as the data capacity of a linka link

•OSPF routing protocol uses bandwidth as its metric. The best path to a network is determined by the path with an accumulation of links that have the highest bandwidth values, or the fastest links.

75© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Router Paths: Equal Cost Load Balancing� You may be wondering what happens if a routing table has

two or more paths with the same metric to the sametwo or more paths with the same metric to the samedestination network.

–When a router has multiple paths to a destination network and the value of that metric (hop count, bandwidth, etc.) is the same, this is known as an equal cost

t i d th t ill f l t l d b l imetric, and the router will perform equal cost load balancing.

� Equal cost metric is a condition where a router has multiple paths to the same destination that all have the same metric

–The router will forward packets using the multiple exit interfaces listed in the routing table.

76© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 40: Nota CCNA Exp 2 - Routing Protocols and Concepts

CRouter Paths: Equal Cost Load Balancing� To solve this dilemma, a router will use Equal Cost Load

Balancing This means the router sends packets over the multipleBalancing. This means the router sends packets over the multipleexit interfaces listed in the routing table.

–per-packet load balancing•( Process Switching)

–per-destination load balancing. •(Fast Switching)•(Fast Switching)

Router(config-if)# ip route-cache Router(config-if)#no ip route-cache

ping 10.0.0.1ping 10.0.0.2 ping 10.0.0.1ping 10.0.0.2

77© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Load balancing with RIPLoad balancing with RIPdebug ip packet

IP k t d b i i

per-packet load balancingIP packet debugging is on

GAD#

*Mar 1 19:10:29.646: IP: tableid=0, s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/1), routed via RIB

*Mar 1 19:10:29.646: IP: s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/1), g=192.168.13.2, len 60, forward

*Mar 1 19:10:30.654: IP: tableid=0, s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/0), routed via RIB

*Mar 1 19:10:30.654: IP: s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/0), g=192.168.15.2, len 60, forward

*Mar 1 19:10:31.654: IP: tableid=0, s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/1), routed via RIB

*Mar 1 19:10:31.654: IP: s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/1), g=192.168.13.2, len 60, forward

*Mar 1 19:10:32.218: IP: s=0.0.0.0 (FastEthernet0/0), d=255.255.255.255, len 604, rcvd 2

*Mar 1 19:10:32.654: IP: tableid=0, s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/0), routed via RIB

*Mar 1 19:10:32.654: IP: s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/0), g=192.168.15.2, len 60, forward

*Mar 1 19:10:33.654: IP: tableid=0, s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/1), routed via RIB

*Mar 1 19:10:33.654: IP: s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/1), g=192.168.13.2, len 60, forward

*Mar 1 19:10:34.654: IP: tableid=0, s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/0), routed via RIB

*Mar 1 19:10:34.654: IP: s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/0), g=192.168.15.2, len 60, forward

*Mar 1 19:10:35.654: IP: tableid=0, s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/1), routed via RIB

*Mar 1 19:10:35.654: IP: s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/1), g=192.168.13.2, len 60, forward

*Mar 1 19:10:35.974: IP: s=192.168.13.1 (local), d=255.255.255.255 (Serial0/1), len 72, sending broad/multicast

*Mar 1 19:10:36.654: IP: tableid=0, s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/0), routed via RIB

*Mar 1 19:10:36.654: IP: s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/0), g=192.168.15.2, len 60, forward

78© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

( ), ( ), g , ,

http://www.cisco.com/en/US/products/ps5763/products_configuration_guide_chapter09186a00802a1fae.html#wp1045020RIB: Router(config-if)#no ip route-cache

Page 41: Nota CCNA Exp 2 - Routing Protocols and Concepts

Load balancing with RIPLoad balancing with RIPdebug ip packet

IP k d b i i

per-destination load balancingIP packet debugging is on

GAD#

*Mar 1 19:14:36.006: IP: tableid=0, s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/0), routed via RIB

*Mar 1 19:14:36.006: IP: s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/0), g=192.168.15.2, len 60, forward

*Mar 1 19:14:36.026: IP: tableid=0, s=192.168.16.2 (Serial0/1), d=192.168.14.2 (FastEthernet0/0), routed via RIB

*Mar 1 19:14:36.026: IP: s=192.168.16.2 (Serial0/1), d=192.168.14.2 (FastEthernet0/0), g=192.168.14.2, len 60, forward

*Mar 1 19:14:37.978: IP: s=0.0.0.0 (FastEthernet0/0), d=255.255.255.255, len 604, rcvd 2

*Mar 1 19:14:44.122: IP: s=0.0.0.0 (FastEthernet0/0), d=255.255.255.255, len 604, rcvd 2

*Mar 1 19:14:46.562: IP: s=192.168.14.1 (local), d=255.255.255.255 (FastEthernet0/0), len 92, sending broad/multicast

*Mar 1 19:14:47.278: IP: s=192.168.15.1 (local), d=255.255.255.255 (Serial0/0), len 72, sending broad/multicast

*Mar 1 19:14:50.266: IP: s=0.0.0.0 (FastEthernet0/0), d=255.255.255.255, len 604, rcvd 2

*Mar 1 19:14:51.958: IP: s=192.168.13.2 (Serial0/1), d=255.255.255.255, len 72, rcvd 2

*Mar 1 19:14:51.962: IP: s=192.168.15.2 (Serial0/0), d=255.255.255.255

Router(config-if)# ip route-cache

79© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negarahttp://www.cisco.com/en/US/products/ps5763/products_configuration_guide_chapter09186a00802a1fae.html#wp1045020RIB:

Router Paths: Un-Equal Cost Load Balancing� Just in case you are wondering, a router can send packets over y g p

multiple networks even when the metric is not the same if it is using a routing protocol that has this capability. This is known as unequal cost load balancing. EIGRP (as well as IGRP) are the onlyq g ( ) yrouting protocols that can be configured for unequal cost load balancing.

� Unequal cost load balancing in EIGRP is not discussed in this� Unequal cost load balancing in EIGRP is not discussed in thiscourse but is covered in CCNP.

80© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 42: Nota CCNA Exp 2 - Routing Protocols and Concepts

� Unequal Cost Load Balancing with EIGRP

� EIGRP Load Balancing E ti t l t l t

What is unequal cost load balancing?

Every routing protocol supports equal costpath load balancing. In addition to that, IGRP and EIGRP also support unequal cost path load balancing.

Use the variance command to instruct the router to include routes with a metric less than n times the minimum metric route for that destination, where n is the number specified by the variancecommand.Example: E-C-A: 20 * 2 = 40. Therefore, E-C-A and E-B-A will be used for load balancing. router eigrp 1

network x.x.x.x variance 2

81© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

variance 2

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a008009437d.shtml

Router Paths and Packet Switching

� Packet forwarding involves two functions:g–Path determination function–Switching function

� Path determination is a process used by a router to pick the best path to a destination

� One of 3 path determinations results from searching f h b hfor the best path

–Directly connected network•The destination IP address of the packet is a host dd th t k thi t 'address on the same network as this router's

interface–Remote network

If th d ti ti IP dd f th k t b l• If the destination IP address of the packet belongsto a remote network, then the packet is forwarded to another router.

–No route determined

82© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

•the packet is discarded

Page 43: Nota CCNA Exp 2 - Routing Protocols and Concepts

R t P th d P k t S it hiRouter Paths and Packet Switching� Switching Function of Router is the process used by a router to switch

a packet from an incoming interface to an outgoing interface on thea packet from an incoming interface to an outgoing interface on thesame router.

� What does a router do with a packet received from one network and destined for another network?

-A packet received by a router will do the following:�Strips off layer 2 headers�Strips off layer 2 headers.�Examines destination IP address located in Layer 3 header to find best route to destination.�Re-encapsulates layer 3 packet into layer 2 frame. �Forwards frame out exit interface.

83© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Router Paths and Packet Switching� As a packet travels from one networking device to another

-The Source and Destination IP addresses NEVER change-The Source & Destination MAC addresses CHANGE as packet is forwarded from one router to the next.

•The Layer 2 data link source address represents the Layer 2 address of the outbound•The Layer 2 data link source address represents the Layer 2 address of the outboundinterface. The Layer 2 destination address represents the Layer 2 address of the next-hop router. If the next hop is the final destination device, it will be the Layer 2 address of that device.•It is very likely that the packet will be encapsulated in a different type of Layer 2 frameIt is very likely that the packet will be encapsulated in a different type of Layer 2 framethan the one in which it was received. For example, the packet might be received by the router on a FastEthernet interface, encapsulated in an Ethernet frame, and forwarded out a serial interface encapsulated in a PPP frame.

-TTL field decrement by one until a value of zero is reached at which point router y pdiscards packet (prevents packets from endlessly traversing the network)

•Demo

84© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 44: Nota CCNA Exp 2 - Routing Protocols and Concepts

Router Paths and Packet Switching

� Path determination and switching function details. PC1a de e a o a d s c g u c o de a s CWants to send something to PC 2 here is part of what happens

Step 1 - PC1 encapsulates packet into a frame. Frame contains R1’s destination MAC address Ethertypes

The 13th and 14th octets of an Ethernet or IEEE802 3 packet (after theor IEEE802.3 packet (after thepreamble) consist of the "Ethernet Type" or "IEEE802.3 Length" field. The "Ethernet Type" values are managed by XEROX. Some assignments are public (see + below), others private.( ), p

85© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

http://www.cavebear.com/archive/cavebear/Ethernet/type.html

Router Paths and Packet SwitchingRouter Paths and Packet SwitchingStep 2 - R1 receives Ethernet frame.

�R1 sees that destination MAC address matches its own MAC.�R1 then strips off Ethernet frame. �R1 Examines destination IP. �R1 consults routing table looking for destination IP.

R1�After finding destination IP in routing table, R1 now looks up next hop IP address.�R1 re-encapsulates IP packet with a new Ethernet frame.

�f the entry is not in the ARP cache, R1 sends an ARP request out its FastEthernet 0/1 interface. R2 sends back an ARP reply.

�R1 forwards Ethernet packet out Fa0/1 interface.

86© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 45: Nota CCNA Exp 2 - Routing Protocols and Concepts

Router Paths and Packet SwitchingRouter Paths and Packet Switching� Path determination and switching function details. PC1 Wants to send something

to PC 2 here is part of what happensStep 3 - Packet arrives at R2Step 3 Packet arrives at R2

�R2 receives Ethernet frame�R2 sees that destination MAC address matches its own MAC�R2 then strips off Ethernet frame

R2R2 then strips off Ethernet frame

�R2 Examines destination IP�R2 consults routing table looking for destination IP�After finding destination IP in routing table, R2 now looks up next hop IPAfter finding destination IP in routing table, R2 now looks up next hop IPaddress�R2 re-encapsulates IP packet with a new data link frame�R2 forwards Ethernet packet out S0/0 interface

�When the interface is a point-to-point serial connection, R2 encapsulates the IP packet into the proper data link frame format used by the exit interface (HDLC, PPP, etc.). In this case, the Layer 2 encapsulation is PPP; therefore, the data link destination address is set to a broadcast. Remember, there are no MAC addresses on serial interfaces.

87© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Router Paths and Packet SwitchingRouter Paths and Packet Switching� PC1 Wants to send something to PC 2 here is part of what happens

Step 4 - Packet arrives at R3 f�R3 receives PPP frame

�R3 then strips off PPP frame�R3 Examines destination IP �R3 consults routing table looking for destination IP�After finding destination IP in routing table, R3 is directly connected to destination via its fast Ethernet interface

�If the entry is not in the ARP cache R3 sends an ARP request out its�If the entry is not in the ARP cache, R3 sends an ARP request out itsFastEthernet 0/0 interface. PC2 sends back an ARP reply with its MAC address.

�R3 re-encapsulates IP packet with a new Ethernet frame�R3 forwards Ethernet packet out Fa0/0 interfacep

Step 5 - IP packet arrives at PC2. Frame is decapsulated & processed by upper layer protocols.

88© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 46: Nota CCNA Exp 2 - Routing Protocols and Concepts

Packet propagation and switching within a routerPacket propagation and switching within a router1

89© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Packet propagation and switching within a router 2

90© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 47: Nota CCNA Exp 2 - Routing Protocols and Concepts

Packet propagation and switching within a router 3

44

91© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Packet propagation and switching within a router

4

92© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 48: Nota CCNA Exp 2 - Routing Protocols and Concepts

Packet propagation and switching within a router 5

93© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

P k t ti d it hi ithi tPacket propagation and switching within a router6

7

94© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

94

Page 49: Nota CCNA Exp 2 - Routing Protocols and Concepts

P k i d i hi i hiPacket propagation and switching within a router

77

95© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Packet propagation and switching within a router

8

96© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 50: Nota CCNA Exp 2 - Routing Protocols and Concepts

P k t ti d it hi ithi tPacket propagation and switching within a router

9

97© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

97

SummarySummary� Routers are computers that specialize in sending data over a network.� Routers are composed of:

-Hardware i.e. CPU, Memory, System bus, Interfaces-Software used to direct the routing processSoftware used to direct the routing process

�IOS�Configuration file

� Routers need to be configured. Basic configuration consists of:-Router name-Router bannerRouter banner-Password(s)-Interface configurations i.e. IP address and subnet mask

� Routing tables contain the following information-Directly connected networks-Remotely connected networks

98© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Remotely connected networks-Network addresses and subnet masks-IP address of next hop address

Page 51: Nota CCNA Exp 2 - Routing Protocols and Concepts

Summary

� Routers determine a packets path to its destination by doing the following

�Receiving an encapsulated frame & examining destination MAC addressMAC address.�If the MAC address matches then Frame is de-encapsulated so that router can examine the destination IP address.�If destination IP address is in routing table or there is a static route then Router determines next hop IP address. Router will re-encapsulate packet with appropriate layer 2 frame and sendre encapsulate packet with appropriate layer 2 frame and sendit out to next destination.�Process continues until packet reaches destination.�Note - only the MAC addresses will change the source and destination IP addresses do not change.

99© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Static Routing

Chapter 2: Routing Protocols and Concepts

Modified by Hasimi Sallehudin

1© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 52: Nota CCNA Exp 2 - Routing Protocols and Concepts

Objectives

� Define the general role a router plays in networks.e e e ge e a o e a ou e p ays e o s

� Describe the directly connected networks, different router interfacesrouter interfaces

� Examine directly connected networks in the routing table and use the CDP protocoltable and use the CDP protocol

� Describe static routes with exit interfaces

� Describe summary and default route

� Examine how packets get forwarded when using static routes

� Identify how to manage and troubleshoot static routes

2© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

General Role of the Router

� Functions of a Routeru c o s o a ou eBest Path SelectionsForwarding packets to destination

� Routers perform packet forwarding by learning about remote networks and maintaining routing information. g g

– The routers primary forwarding decision is based on Layer 3 information, the destination IP address.– The router's routing table is used to find the best match between the destination IP of a packet and a network address in the routing table. – The routing table will ultimately determine the exit interface to forward the packet and the router will encapsulate that packet in the appropriated data link frame for that outgoing interface

3© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

the appropriated data link frame for that outgoing interface.

Page 53: Nota CCNA Exp 2 - Routing Protocols and Concepts

General Role of the Router

� Introducing the Topologyoduc g e opo ogy– The figure shows the topology used in this chapter. – 3 1800 series routers connected via WAN links– Each router connected to a LAN represented by a switch and a PC

4© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

General Role of the Router

� Connections of a Router for WAN -A router has a DB-60 port that can support 5 different cabling standards–Newer routers support the smart serial ppinterface that allows for more data to be forwarded across fewer cable pins.

� Connections of a Router for Ethernet-2 types of connectors can be used: Straight through and Cross-over �Straight through used to connect:Straight through used to connect:

-Switch-to-Router, Switch-to-PC, Hub-to-PC, Hub-to-Server

�Cross-over used to connect (pin 1 connectedCross-over used to connect (pin 1 connectedto pin 3, and pin 2 connected to pin 6):

-Switch-to-Switch, PC-to-PC, Switch-to-Hub, Hub-to-Hub, Router-to-Router, PC-

5© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

, , ,Router

Page 54: Nota CCNA Exp 2 - Routing Protocols and Concepts

General Role of the Router in COD

� Smart Serial cables: DCE and DTE S a Se a cab es C a d-Use straight cable to connect between the DTE and DCE.. DCE and DTE Adapter

� Ethernet cables:� Cross-over cable: RED cable� Roll-over cable: flat cables

� Straight cable: all other cables

http://www.csdata.com/csdonline/customer/home.php

6© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Serial Connectors

DTEDCEDCE

DTE DTEDCE

DTE DTEDCE

� In our labs we will use serial DTE/DCE cables (no CSU/DSU) with a DTE cable connected to one router and

DCE bl t d t th th t

7© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

a DCE cable connected to the other router.

Page 55: Nota CCNA Exp 2 - Routing Protocols and Concepts

Interfaces

� Examining Router Interfacesa g oute te aces-Show IP router command – used to view routing table-Show Interfaces command – used to show status of an interface-Show IP Interface brief command – used to show a portion of

the interface information on a condensed formatSh i fi d d t h fi ti-Show running-config command – used to show configuration

file in RAM

8© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Interfaces

� Configuring an Ethernet interfaceCo gu g a t e et te ace-By default all serial and Ethernet interfaces are down-To enable an interface use the No Shutdown command

•The show ip routecommand is used to display the routing table. •Initially, the routing table is empty if no interfaces have b fi dbeen configured.•Static routes and dynamic routes will not be added to th ti t bl til ththe routing table until theappropriate local interfaces have been configured on the router

9© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

the router.

Page 56: Nota CCNA Exp 2 - Routing Protocols and Concepts

Verifying Ethernet interfaceVerifying Ethernet interface- Show interfaces - command shows the status and gives a detailed description for all interfaces on the routerp– Show interfaces fastEthernet 0/0 – command used to show status of fast Ethernet port

R1#show interfaces fastethernet 0/0•R1#show interfaces fastethernet 0/0•FastEthernet0/0 is administratively down, line protocol is down• Administratively down means that the interface is currently in the shutdown mode, or turned off. •Line protocol is down means in this case that the interface is not receiving a carrier signal from•Line protocol is down means, in this case, that the interface is not receiving a carrier signal froma switch or the hub. This condition may also be due to the fact that the interface is in shutdown mode• You will notice that the show interfaces command does not show any IP addresses on R1's interfaces The reason for this is because we have not yet configured IP addresses on any of theinterfaces. The reason for this is because we have not yet configured IP addresses on any of theinterfaces.

10© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

InterfacesInterfaces� Verifying Ethernet interface

– Show run –Show run• command displays the current configuration file that the router is using. Configuration commands are temporarily stored in the running configuration file and implemented immediately by the routerand implemented immediately by the router.•However, using show running-config is not necessarily the best way to verify interface configurations.

-Show ip interface brief –-can be used to see a portion of the interface information in a condensed format.

11© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 57: Nota CCNA Exp 2 - Routing Protocols and Concepts

Configuring an Ethernet interfaceConfiguring an Ethernet interfaceBy default, all router interfaces are shutdown. To enable this interface, use the no shutdown command, which changes the interface from administratively down to upinterface from administratively down to up.

R1(config)#interface fastethernet 0/0R1(config-if)#ip address 172.16.3.1 255.255.255.0R1(config-if)#no shutdown

The following message is returned from the IOS:

*Mar 1 01:16:08.212: %LINK-3-UPDOWN: Interface FastEthernet0/0, changed state to up*Mar 1 01:16:09.214: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to upp , g p

–The first changed state to up message indicates that, physically, the connection is good. If you do not get this first message, be sure that the interface is properly connected to g , p p ya carrier signal from switch or a hub. –The second changed state to up message indicates that the Data Link layer is operational.

• However WAN interfaces in a lab environment require

12© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

• However, WAN interfaces in a lab environment requireclocking on one side of the link. If you do correctly set the clock rate, then line protocol will not change to up.

Configuring an Ethernet interfaceConfiguring an Ethernet interface� Unsolicited Messages from IOSg� The IOS often sends unsolicited messages.

� As you can see in the figure, sometimes these messages will occur when you are in the middlemessages will occur when you are in the middleof typing a command, such as configuring a description for the interface.

–The IOS message does not affect the command, but it can cause you to lose your place when typing.

� In order to keep the unsolicited output separateIn order to keep the unsolicited output separatefrom your input, enter line configuration mode for the consoled port and add the loggingsynchronous command, as shown. You will see that messages returned by IOS no longerthat messages returned by IOS no longerinterfere with your typing.

13© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 58: Nota CCNA Exp 2 - Routing Protocols and Concepts

InterfacesInterfaces� Verifying Ethernet interface

-Show interfaces fastEthernet 0/0� Reading the Routing Table

–Now look at routing table shown in the figure. Notice R1 now has a "directly connected"FastEthernet 0/0 interface a new network. –The interface was configured with the 172.16.3.1/24 IP address which makes it a member of the 172.16.3.0/24 network.

� 172.16.0.0/24 is subnetted, 1 subnets� C 172.16.3.0 is directly connected, FastEthernet0/0

–The C at the beginning of the route indicates that this is a directly connected network. In other words, R1 has an interface that belongs to this networknetwork.–The /24 subnet mask for this route is displayed in the line above the actual route.

14© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

InterfacesInterfaces� Reading the Routing Table� 172.16.0.0/24 is subnetted, 1 subnets172.16.0.0/24 is subnetted, 1 subnets

–Having a single route represent an entire network of host IP addresses makes thenetwork of host IP addresses makes therouting table smaller, with fewer routes, which results in faster routing table lookups.

•It means that this route matches all•It means that this route matches allpackets with a destination address belonging to this network.

–The routing table could contain all 254 i di id l h t IP dd f thindividual host IP addresses for the172.16.3.0/24 network, but that is an inefficient way of storing addresses.

15© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 59: Nota CCNA Exp 2 - Routing Protocols and Concepts

InterfacesInterfaces� Verifying Ethernet interface

show interfaces fastethernet 0/0show ip interface brief

� The show interfaces fastethernet 0/0 commandin the figure now showsin the figure now shows

–The interface is up, and the line protocol is up. The no shutdown command changed the interface from administratively down to up. –Notice that the IP address is now displayed.

� The command show ip interface brief in the figure shows that the interface is up, and the li t l i (i d d f t)line protocol is up. (in a condensed format)

� Typically, the router's Ethernet or FastEthernet interface will be the default gateway IP address for any devices on that LANfor any devices on that LAN.

–For example, PC1 would be configured with a IP address belonging to the 172.16.3.0/24 network, with the default gateway IP address

16© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

g y172.16.3.1.–172.16.3.1 is router R1's FastEthernet IP address.

Ethernet Interfaces Participate in ARPEthernet Interfaces Participate in ARP� A router's Ethernet interface participates

in a LAN network just like any other device on that networkdevice on that network.

–This means that these interfaces have a Layer 2 MAC address, as shown in the figure. The show interfaces command displays the MAC dd f th Eth t i t fMAC address for the Ethernet interfaces.–If a router has a packet destined for a device on a directly connected Ethernet network, it checks the ARP table for an entry, ywith that destination IP address in order to map it to the MAC address.

17© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 60: Nota CCNA Exp 2 - Routing Protocols and Concepts

Interfaces

� Configuring a Serial interface� Configuring a Serial interface-Enter interface configuration mode-Enter in the ip address and subnet maskEnter in the ip address and subnet mask-Enter in the no shutdown command

� Example:Example:-R1(config)#interface serial 0/0/0-R1(config-if)#ip address 172.16.2.1 255.255.255.0( g ) p-R1(config-if)#no shutdown

18© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Interfaces� R1(config)#interface serial 0/0/0� R1(config if)#ip address 172 16 2 1 255 255 255 0� R1(config-if)#ip address 172.16.2.1 255.255.255.0� R1(config-if)#no shutdown

� R2(config)#interface serial 0/0/0� R2(config-if)#ip address 172.16.2.2 255.255.255.0� R2(config-if)#no shutdown

–There is no requirement that both ends of the serial link use the same interface, (0/0/0, 0/0/1, 0/1/0, 0/1/1, ….)–in this case, Serial 0/0/0. However, because both interfaces are members of the same network, they both must have IP addresses that belong to the 172.16.2.0/24 network.If we now issue the show interfaces serial 0/0/0 command on either router we still see that–If we now issue the show interfaces serial 0/0/0 command on either router, we still see that

the link is up/down.

� R2#show interfaces serial 0/0/0� Serial0/0/0 is up, line protocol is downp, p

– The physical link between R1 and R2 is up because both ends of the serial link have been configured correctly with an IP address/mask and enabled with the no shutdown command. – However, the line protocol is still down. This is because the interface is not receiving a clock signal.

19© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

– There is still one more command that we need to enter, the clock rate command, on the router with the DCE cable. The clock rate command will set the clock signal for the link.

Page 61: Nota CCNA Exp 2 - Routing Protocols and Concepts

InterfacesStep 1 Step 3

Nothing is configured Setup “no shut”

Step 2 Step 4

Setup IP but not “no shut” Configured the clock rate

20© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

� Examining Router Interfaces� Examining Router Interfaces-Physically connecting a WAN Interface. A WAN Physical Layer connection has sides:-A WAN Physical Layer connection has sides:

�Data Circuit-terminating Equipment (DCE) – This is the service provider. CSU/DSU is a DCE device.

� The CSU/DSU (DCE device) is used to convert the data from the router (DTE device) into a form acceptable to the WAN service provider. �a DCE device such as a CSU/DSU will provide the clock.

�Data Terminal Equipment (DTE) – Typically the router is the DTE device.

Up-to-date technology

Cisco 1-Port T1/Fractional T1

21© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Cisco 1 Port T1/Fractional T1DSU/CSU WAN Interface Card (WIC-1DSU-T1-V2=)

Page 62: Nota CCNA Exp 2 - Routing Protocols and Concepts

Interfaces- What is the significant of the information 1?

� For serial links that are directly interconnected, as in a lab environment, one side of a connection must be considered a DCE and provide a clocking signal.

� You can also distinguish DTE from DCE –1) by looking at the connector between the two cables. The DTE cable has a male connector whereas the DCEThe DTE cable has a male connector, whereas the DCEcable has a female connector.–2) If a cable is connected between the two routers, you can use the show controllers command to determinecan use the show controllers command to determinewhich end of the cable is attached to that interface.

R1#show controllers serial 0/0/0Interface Serial0/0/0Hardware is PowerQUICC MPC860DCE V.35, no clock<output omitted>

22© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Interfaces

� Once the cable is attached, the clock can now be set with the clock rate commandthe clock rate command.

–The available clock rates, in bits per second, are 1200, 2400, 9600, 19200, 38400, 56000, 64000,72000, 125000, 148000, 500000, 800000, 1000000 1300000 2000000 and 40000001000000, 1300000, 2000000, and 4000000.–Some bit rates might not be available on certain serial interfaces.

� R1(config)#interface serial 0/0� R1(config-if)#clock rate 64000

01 10 28 %LINEPROTO 5 UPDOWN Li t l� 01:10:28: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed state to up

� Note: If a router's interface with a DTE cable is configured� Note: If a router s interface with a DTE cable is configuredwith the clock rate command, the IOS will disregard the command and there will be no ill effects.

–Use the “show controllers serial 0/0/0” to find out whether it is a DTE or DCE cable

23© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

find out whether it is a DTE or DCE cable.

Page 63: Nota CCNA Exp 2 - Routing Protocols and Concepts

TestingVerifying the Serial Interface ConfigurationR1#show interfacesR1#show ip interface briefR1#ping 172.16.2.2R1#show ip route

24© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

R ti T bl C tRouting Table Concepts� The show ip route command reveals the content of the routing table.

Th i f ti t bl i t id th t ith th t–The main purpose of a routing table is to provide the router with paths todifferent destination networks.

� The routing table consists of a list of "known" network addressesdi tl t d–directly connected,

–configured statically, –learned dynamically.

� POP Quiz:– Can R1 ping R2?– Can PC1 ping PC2?p g

25© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 64: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table ConceptsRouting Table Concepts� Purpose of the debug ip routing command

�Allows you to view changes that the router performs when adding orAllows you to view changes that the router performs when adding orremoving routes in real time

13

enable debugging with the debug ip routing command Configuring the IP address and Subnet Mask

disable interfaces with the shutdown command.

g g

4 Check the routing table

2 Check the routing table

5 Disable debug ip routing by using

26© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

5 routing by usingeither the “undebug ip routing” command or the “undebug all” command.

Never use the debug all command on the production router.

Routing Table and CDP Protocol

� When a router only has its interfaces configured &no other routing protocols are configured then:

-The routing table contains only the directly connected networks-Only devices on the directly connected networks are reachable

POP Quiz: The output in this figure verifies that all Whypingsfailed?

p gconfigured interfaces are "up" and "up".

27© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 65: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table and CDP Protocol

� When a router only has its interfaces configured, and the ti t bl t i th di tl t d t k b trouting table contains the directly connected networks but

no other routes, only devices on those directly connected networks are reachable.

–R1 can communicate with any device on the 172 16 3 0/24R1 can communicate with any device on the 172.16.3.0/24and 172.16.2.0/24 networks.–R2 can communicate with any device on the 172.16.1.0/24, 172.16.2.0/24, and 192.168.1.0/24 networks.

/–R3 can communicate with any device on the 192.168.1.0/24and 192.168.2.0/24 networks.

28© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing Table and CDP ProtocolRouting Table and CDP Protocol� Checking each route in turn

–The ping command is used to check end to end connectivity–Ping 172.16.3.1 failed

•Route does not match any route in the routing table

–Ping 192.168.1.1 succeed•192.168.1.0/24, matches the first 24 bits of the destination IP address

29© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 66: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table and CDP Protocol� Purpose of CDP

–Cisco Discovery Protocol (CDP) is a powerfulnetwork monitoring and troubleshooting tool.

•CDP runs at the Data Link layer connecting the physical di t th l t l (ULP )media to the upper-layer protocols (ULPs).

•Because CDP operates at the Data Link layer, two or more Cisco network devices, such as routers that support different Network layer protocols (for example, IP and Novell IPX), can y p ( p , ),learn about each other.

–A layer 2 cisco proprietary tool used to gather information about other directly connected Cisco devices.

•enables you to access a summary of protocol and address information about Cisco devices that are directly connected.

–the types of devices that are connected, th i t f th t d t–the interfaces they are connected to,

–the interfaces used to make the connections, –the model numbers of the devices.

30© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

–……..

Routing Table and CDP Protocol� Concept of neighbors

-2 types of neighbors�Layer 3 neighbors

� At Layer 3, routing protocols consider neighbors to be d i th t h th t k dddevices that share the same network address space.

� R1 and R2 are neighbors. Both are members of the 172.16.1.0/24 network. � R2 and R3 are also neighbors because they both shareR2 and R3 are also neighbors because they both sharethe 192.168.1.0/24 network. � But R1 and R3 are not neighbors because they do not share any network address space.

�Layer 2 neighbors�Layer 2 neighbors�CDP operates at Layer 2 only. Therefore, CDP neighbors are Cisco devices that are directly connected physically and share the same data link.

»R1 and S1 are CDP neighbors.»R1 and R2 are CDP neighbors.»R2 and S2 are CDP neighbors.R2 d R3 CDP i hb

Notice the difference between Layer 2 and Layer 3 neighbors. The switches are not neighbors to the routers at Layer 3, because the switches are operating at Layer 2 only

31© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

»R2 and R3 are CDP neighbors.»R3 and S3 are CDP neighbors.

the switches are operating at Layer 2 only.However, the switches are Layer 2 neighbors to their directly connected routers.

Page 67: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table and CDP Protocol� CDP is on by default.

–CDP exchanges hardware and software–CDP exchanges hardware and softwaredevice information with its directly connected CDP neighbors.

� CDP show commands�Show cdp neighbors command

-Displays the following information:�Neighbor device ID�Local interface�Local interface�Holdtime value, in seconds�Neighbor device capability code�Neighbor hardware platform�Neighbor remote port ID

�Show cdp neighbors detail command-It can also reveals the IP address of a neighboring device

–knowing the IP address of the CDP neighbor is often allows you to telnet into that device.

• and a lot more– IOS version

32© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

– Platform– …………

Routing Table and CDP Protocol

� Disabling CDPsab g C– CDP be a security risk

• Because some IOS versions send out CDP advertisements by default, it is important to know how to disable CDP.

–If you need to disable CDP globally, for the entire device, use this command:this command:

• Router(config)#no cdp run

–If you want to use CDP but need to stop CDP advertisements on a particular interface, use this command:

• Router(config-if)#no cdp enable

33© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 68: Nota CCNA Exp 2 - Routing Protocols and Concepts

Static Routes

� A router can learn about remote networks in one of two ways:y–Manually, from configured static routes–Automatically, from a dynamic routing protocol

D i ti t l i t d d i th t h t•Dynamic routing protocols are introduced in the next chapter.

� Purpose of a static routeA manually configured route used when routing from a network to a stub–A manually configured route used when routing from a network to a stub

network

•A stub network is a network accessed by a single route.•For an example, here we see that any network attached to R1 would only have one way to reach other destinations, whether to networks attached to R2 orwhether to networks attached to R2 orto destinations beyond R2. •Therefore, network 172.16.3.0 is a stub network and R1 is a stub router. Running a routing protocol between R1

34© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

•Running a routing protocol between R1and R2 is a waste of resources

Static Routes

� IP route commandoute co a d�To configure a static route use the following command: ip route�Example:

-Router(config)# ip route network-address subnet-mask {ip-address | exit-interface }

35© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 69: Nota CCNA Exp 2 - Routing Protocols and Concepts

Static route operation Example: Fly from Chicago to LA

Chicago

O’Hare

LosAngeles

Chi � O’H Ai � L A lChicago � O’Hare Airport � Los Angeles

RTR(config)# ip route prefix mask {address | interface}

36© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

( g) p p f { | f }O’Hare

LosAngeles

Static Routes

� Remember R1 knows about its directlyyconnected networks.

–These are the routes currently in its routing table.

� The remote networks that R1 does not know about are:

–172.16.1.0/124 - The LAN on R2–192.168.1.0/24 - The serial network between R2 and R3–192.168.2.0/24 - The LAN on R3

37© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 70: Nota CCNA Exp 2 - Routing Protocols and Concepts

Static Routes

�R1(config)#ip route 172 16 1 0 255 255 255 0 172 16 2 2� Dissecting static route syntax

�ip route - Static route command172 16 1 0 D ti ti t k dd

�R1(config)#ip route 172.16.1.0 255.255.255.0 172.16.2.2

�172.16.1.0 – Destination network address�255.255.255.0 - Subnet mask of destination network�172.16.2.2 - Serial 0/0/0 interface IP address on R2, which is the "next-hop" to this network

� show ip route output–S - Routing table code for static route172 16 1 0 N t k dd f th t–172.16.1.0 - Network address for the route

–/24 - Subnet mask for this route; this is displayed in the line above, known as the parent route, and discussed in Chapter 8–[1/0] - Administrative distance and metric for the static route (explained in a later chapter)–via 172.16.2.2 - IP address of the next-hop router, the IP address of R2's Serial 0/0/0 interface

38© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

interface

Static Routes

�R1(config)#ip route 172 16 1 0 255 255 255 0 172 16 2 2� show ip route output

–S - Routing table code for static route172 16 1 0 N t k dd f th t

�R1(config)#ip route 172.16.1.0 255.255.255.0 172.16.2.2

–172.16.1.0 - Network address for the route–/24 - Subnet mask for this route; this is displayed in the line above, known as the parent route, and discussed in Chapter 8–[1/0] - Administrative distance and metric for the static route (explained in a later chapter)–via 172.16.2.2 - IP address of the next-hop router, the IP address of R2's Serial 0/0/0 interfaceinterface

39© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 71: Nota CCNA Exp 2 - Routing Protocols and Concepts

Static Routes

� Configuring routes to 2 or more remote networksCo gu g outes to o o e e ote et o sUse the following commands for R1

-R1(config)#ip route 192.168.1.0 255.255.255.0 172.16.2.2-R1(config)#ip route 192.168.2.0 255.255.255.0 172.16.2.2

40© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Static Routes

� Zinin’s 3 routing principlesf�Principle 1: "Every router makes its decision alone, based on the information it has

in its own routing table.“� R1 has three static routes in its routing table and makes forwarding decisions based solely upon the information in the routing table. � R1 does not consult the routing tables in any other routers. � Making each router aware of remote networks is the responsibility of the network administrator.

�Principle 2: "The fact that one router has certain information in its routing table does�Principle 2: The fact that one router has certain information in its routing table doesnot mean that other routers have the same information.“

� The network administrator would be responsible for ensuring that the next-hop router also has a route to this network� Using Principle 2 we still need to configure the proper routing on the other� Using Principle 2, we still need to configure the proper routing on the otherrouters (R2 and R3) to make sure that they have routes to these three networks.

�Principle 3: "Routing information about a path from one network to another does not provide routing information about the reverse, or return path.“

M f h i i k i bidi i l Thi h� Most of the communication over networks is bidirectional. This means thatpackets must travel in both directions between the end devices involved. � Using Principle 3 as guidance, we will configure proper static routes on the other routers to make sure they have routes back to the 172.16.3.0/24 network.

41© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 72: Nota CCNA Exp 2 - Routing Protocols and Concepts

Static Routes

42© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Static Routes with next-hop IP address

� Resolving to an Exit Interface-Recursive route lookup - Occurs when the router has to perform multiple lookups in the routing table before forwarding a packet. A static route that forwards all packets to the next-hop IP address goes through the following process (reclusive route lookup)

� (Step 1) The router first must match static route’s destination IP address with the Next hop addressp

� The packet's destination IP address is matched to the static route 192.168.2.0/24 with the next-hop IP address 172.16.2.2.

� (Step 2) The next hop address is then matched to an exit interface(Step 2) The next hop address is then matched to an exit interface�The next-hop IP address of the static route, 172.16.2.2, is matched to the directly connected network 172.16.2.0/24 with the exit interface of Serial 0/0/0.

43© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 73: Nota CCNA Exp 2 - Routing Protocols and Concepts

Static Routes with Exit InterfacesStatic Routes with Exit Interfaces� Configuring a Static route with an Exit

InterfaceS i fi d i h i i f-Static routes configured with an exit interface

are more efficient because the routing–The routing table can resolve the exit interface in a single search instead of 2 searchesin a single search instead of 2 searches

� If the static route cannot be resolved to an exit interface, the static route is removed from th ti t blthe routing table

–Notice from the debug output that all three static routes were deleted when the Serial 0/0/0 interface was shut downinterface was shut down.–They were deleted because all three static routes were resolved to Serial 0/0/0. However the static routes are still in the R1's–However, the static routes are still in the R1 s

running configuration. If the interface comes back up (is enabled again with no shutdown), the IOS routing table process will reinstall these t ti t b k i t th ti t bl

44© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

static routes back into the routing table.

Static Routes with Exit Interfaces� Modifying Static routes

�Existing static routes cannot be modified. The old static route must be deleted by placing no in front of the ip routeExample:�Example:

-no ip route 192.168.2.0 255.255.255.0 172.16.2.2�A new static route must be rewritten in the configuration�A new static route must be rewritten in the configuration

R1(config)# no ip route 192.168.2.0 255.255.255.0 172.16.2.2R1(config)#ip route 192.168.2.0 255.255.255.0 serial 0/0/0

45© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 74: Nota CCNA Exp 2 - Routing Protocols and Concepts

Static Routes with Exit Interfaces

� Verifying the Static Route Configuration-Use the following commands

�Step 1 show running-config�Step 2 verify static route has been entered correctlyStep 2 verify static route has been entered correctly�Step 3 show ip route�Step 4 verify route was configured in routing tableSt 5 i i d t if k t�Step 5 issue ping command to verify packets can

reach destination and that Return path is working

46© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Static route operation

Both types of the routes all have distance of 1

47© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

all have distance of 1and metric of 0.

Page 75: Nota CCNA Exp 2 - Routing Protocols and Concepts

Static Routes with Exit InterfacesStatic Routes with Exit Interfaces� Ethernet interfaces and ARP.

– If a static route is configured on an Ethernet linkIf a static route is configured on an Ethernet link•If the packet is sent to the next-hop router then…

–the destination MAC address will be the address of the next–the destination MAC address will be the address of the nexthop’s Ethernet interface–This is found by the router consulting the ARP table.

»If an entry isn’t found then an ARP request will be sent out

R1(config)#ip route 192 168 2 0 255 255 255 0 fa 0/1R1(config)#ip route 192.168.2.0 255.255.255.0 fa 0/1

48© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Static Routes with Exit InterfacesStatic Routes with Exit Interfaces

B t t t l it i t f ith Eth t i t fR1(config)#ip route 192.168.2.0 255.255.255.0 fastethernet 0/1� Best not to use only an exit interface with Ethernet interfaces.� Router will have difficulty determining the destination MAC address.� With Ethernet networks many different devices can be sharing the� With Ethernet networks, many different devices can be sharing the

same multiaccess network, including hosts and even multiple routers. � Router will not have sufficient information to determine which device

is the next-hop deviceis the next hop device.� Use both the next-hop interface and the exit interface for

Ethernet exit interfaces.O l i l t l k d d� Only a single route lookup now needed.

R1(config)#ip route 192.168.2.0 255.255.255.0 fastethernet 0/1 172.16.2.2

The routing table entry for this route would be:

S 192.168.2.0/24 [1/0] via 172.16.2.2 FastEthernet0/1

49© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 76: Nota CCNA Exp 2 - Routing Protocols and Concepts

Summary and Default Route

� Summarizing routes reduces the size of the routingg gtable.

� Route summarization is the process of combining a fnumber of static routes into a single static route.

–For example, the networks 10.0.0.0/16, 10.1.0.0/16, 10.2.0.0/16, 10.3.0.0/16, 10.4.0.0/16, 10.5.0.0/16, all the way0 0 0/ 6, 0 3 0 0/ 6, 0 0 0/ 6, 0 5 0 0/ 6, a e aythrough 10.255.0.0/16 can be represented by a single network address: 10.0.0.0/8.

� Multiple static routes can be summarized into a single� Multiple static routes can be summarized into a singlestatic route if:

–The destination networks can be summarized into a singlegnetwork address, and –The multiple static routes all use the same exit-interface or next-hop IP address

50© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

e t op add ess

Calculating a summary route

� Here's the process of creating the summary route 172 16 1 0/22 as sho n in the fig re172.16.1.0/22, as shown in the figure:

1. Write out the networks that you want to summarize in binary.

2. To find the subnet mask for summarization, start with the left-most bitthe left-most bit.

3. Work your way to the right, finding all the bits that match consecutively.

4. When you find a column of bits that do not match, stop. You are at the summary boundary.p y y

5. Now, count the number of left-most matching bits, which in our example is 22. This number becomes your subnet mask for the summarized route, /22 or 255.255.252.0

6 To find the network address for summarization copy6. To find the network address for summarization, copythe matching 22 bits and add all 0 bits to the end to make 32 bits.

� By following these steps, we can discover that the 3 static routes on R3 can be summarized into a singlestatic routes on R3 can be summarized into a singlestatic route, using the summary network address of 172.16.0.0 255.255.252.0:ip route 172.16.0.0 255.255.252.0 Serial0/0/1

51© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 77: Nota CCNA Exp 2 - Routing Protocols and Concepts

Example: Calculating a summary route

� Which address can be used toWhich address can be used tosummarize networks 172.168.0.0 /24 through 172.168.7.0 /24?g

� 10101100 10101000 00000000 00000000� 10101100 10101000 00000001 00000000� 10101100 10101000 00000010 00000000� 10101100 10101000 00000011 00000000

10101100 10101000 00000100 00000000� 10101100 10101000 00000100 00000000� 10101100 10101000 00000101 00000000� 10101100 10101000 00000110 00000000� 10101100 10101000 00000110 00000000� 10101100 10101000 00000111 00000000

Answer:52© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

� Answer:

Example: Calculating a summary route

� Which address can be� Which address can beused to summarize networks � 11000000 00000001 00000001 00000000• 192.1.1.0/27• 192.1.1.32/27• 192 1 1 64/28

11000000 00000001 00000001 00000000� 11000000 00000001 00000001 00100000� 11000000 00000001 00000001 01000000

• 192.1.1.64/28• 192.1.1.80/28• 192.1.1.96/29

� 11000000 00000001 00000001 01010000� 11000000 00000001 00000001 01100000� 11000000 00000001 00000001 01101000

• 192.1.1.104/29• 192.1.1.112/29• 192 1 1 120/29

11000000 00000001 00000001 01101000� 11000000 00000001 00000001 01110000� 11000000 00000001 00000001 01111000

192.1.1.120/29

Answer:53© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

� Answer:

Page 78: Nota CCNA Exp 2 - Routing Protocols and Concepts

SSummary Route� Configuring a summary route

–Step 1: Delete the current static routeR3(config)#no ip route 172.16.1.0 255.255.255.0 serial0/0/1R3(config)#no ip route 172.16.2.0 255.255.255.0 serial0/0/1R3(config)#no ip route 172.16.3.0 255.255.255.0 serial0/0/1

–Step 2: Configure the summary static route•R3(config)#ip route 172 16 0 0 255 255 252 0 serial0/0/1R3(config)#ip route 172.16.0.0 255.255.252.0 serial0/0/1

–Step 3: Verify the new static route •show ip route ping

54© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Summary Route

� Static routes and subnet masks–The routing table lookup process will use the most specific matchwhen comparing destination IP address and subnet mask

For example what if we had the following two static routes in the–For example, what if we had the following two static routes in therouting table

•172.16.0.0/24 is subnetted, 3 subnetsS 172 16 1 0 i di tl t d S i l0/0/0 d•S 172.16.1.0 is directly connected, Serial0/0/0 and

•S 172.16.0.0/16 is directly connected, Serial0/0/1

–Consider a packet with the destination IP address 172.16.1.10. ThisIP address matches both routes.

•The routing table lookup process will use the most-specific match. •Because 24 bits match the 172 16 1 0/24 route and only 16 bits ofBecause 24 bits match the 172.16.1.0/24 route, and only 16 bits ofthe 172.16.0.0/16 route match, the static route with the 24 bit match will be used. •This is the longest match

55© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

•This is the longest match.

Page 79: Nota CCNA Exp 2 - Routing Protocols and Concepts

Default Route

� Default Static Route�This is a route that will match all packets.�Like route summarization this will help reducethe size of the routing table

� Default static routes are used:–When no other routes in the routing table match the packet's destination IP address. A common use is when connecting a company's edge router to the ISPwhen connecting a company s edge router to the ISPnetwork.–When a router has only one other router to which it is connected. This condition is known as a stub router.

� Configuring a default static route�Similar to configuring a static route. Except that destination IP address and subnet mask are all zeros�Example:

-Router(config)#ip route 0.0.0.0 0.0.0.0 [ it i t f | i dd ]

56© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

[exit-interface | ip-address ]

Summary and Default Route� R1 is a stub router.

It i l t d t R2–It is only connected to R2.–Currently R1 has three static routes, which are used to reach all of the remote networks in our topology. –All three static routes have the exit interface Serial 0/0/0, forwarding packets, g pto the next-hop router R2.

� R1 is an ideal candidate to have all f it t ti t l d bof its static routes replaced by a

single default route. –First, delete the three static routes,–Next, configure the single default static route using the same Serial 0/0/0 exit interface

57© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

interfaceR1(config)#ip route 0.0.0.0 0.0.0.0 serial 0/0/0

Page 80: Nota CCNA Exp 2 - Routing Protocols and Concepts

Static Routes and Packet ForwardingStatic Routes and Packet Forwarding� Verify the change to the routing table y g g

with the show ip route command� S* 0.0.0.0/0 is directly connected, Serial0/0/0

–Note the * or asterisk next to the S–Note the or asterisk next to the S.•As you can see from the Codes table in the figure, the asterisk indicates that this static route is a candidate default route.

–The key to this configuration is the /0 mask.

•We previously said that it is the subnet•We previously said that it is the subnetmask in the routing table that determines how many bits must match between the destination IP address of the packet and th t i th ti t blthe route in the routing table.•A /0 mask indicates that zero or no bits are needed to match.

58© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

S lf t t St ti d t ti d f lt tSelf test: Static and static default route� Can you use both static andCa you use bo s a c a d

static default route to configure the communication b t b th LANS d thbetween both LANS and thecommunication to the Internet.Internet.

-Only 3 statement of static route needed to setup the network.

1 t ti t-1 static route-2 default static route

WinterPark(config)# ip route 0.0.0.0 0.0.0.0 192.168.146.1Altamonte(config)# ip route 10.0.234.0 255.255.255.0 192.168.146.2Alt t ( fi )# i t 0 0 0 0 0 0 0 0 0/1

59© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Altamonte(config)# ip route 0.0.0.0 0.0.0.0 s0/1

Page 81: Nota CCNA Exp 2 - Routing Protocols and Concepts

Static Routes and Packet Forwarding

� Troubleshooting a Missing Routeoub es oo g a ss g ou e

� Tools that can be used to isolate routing problems include:include:

-Ping– tests end to end connectivity-Traceroute– used to discover all of the hops (routers) along the

Layer 3p ( ) g

path between 2 points-Show IP route– used to display routing table & ascertain forwarding processforwarding process-Show ip interface brief- used to show status of router interfaces-Show cdp neighbors detail– used to gather configuration

Layer 2Show cdp neighbors detail used to gather configuration

information about directly connected neighbors

60© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Static Routes and Packet Forwarding

� Solving a Missing RouteSo g a ss g ou e

� Finding a missing or mis-configured route requires methodically using the correct toolsmethodically using the correct tools

-Start with PING. If ping fails then use traceroute to determine where packets are failing to arrive- Than trace route

� Issue: show ip route to examine routing table.-If there is a problem with a mis-configured static route remove the static route then reconfigure the new static route

61© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 82: Nota CCNA Exp 2 - Routing Protocols and Concepts

SummarySummary� Routers

-Operate at layer 3p y-Functions include best path selection & forwarding packets

� Connecting NetworksWANs

Serial cables are connected to router serial ports. In the lab environment clock rates must be configured for DCEt e ab e o e t c oc ates ust be co gu ed o C

LANsStraight through cables or cross over cables are used to connect to fastethernet port (The type of cable used dependsconnect to fastethernet port. (The type of cable used dependson what devices are being connected)

� Cisco Discovery ProtocolA layer 2 proprietary protocolA layer 2 proprietary protocolUsed to discover information about directly connected Ciscodevices

62© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

SummarySummary� Static Routes

-This is a manually configured path that specifies how the routerThis is a manually configured path that specifies how the routerwill get to a certain point using a certain path.

� Summary static routes-This is several static routes that have been condensed into a-This is several static routes that have been condensed into asingle static route.

� Default routeIt is the route packets use if there is no other possible match for-It is the route packets use if there is no other possible match for

their destination in the routing table.� Forwarding of packets when static route is used

Zi i ’ 3 ti i i l d ib h k t f d d-Zinin’s 3 routing principles describe how packets are forwarded� Troubleshooting static routes may require some of the following

commands:-Ping-Traceroute-Show IP route

63© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

-Show ip interface brief -Show cdp neighbors detail

Page 83: Nota CCNA Exp 2 - Routing Protocols and Concepts

Introduction to Dynamic Routing Protocolg

Chapter 3: Routing Protocols and ConceptsModified by Hasimi Sallehudin

1© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Objectives

� Describe the role of dynamic routing protocols andesc be e o e o dy a c ou g p o oco s a dplace these protocols in the context of modern network design.

� Identify several ways to classify routing protocols.

� Describe how metrics are used by routing protocolsDescribe how metrics are used by routing protocolsand identify the metric types used by dynamic routing protocols.

� Determine the administrative distance of a route and describe its importance in the routing process.

� Identify the different elements of the routing table.

2© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 84: Nota CCNA Exp 2 - Routing Protocols and Concepts

Dynamic Routing Protocols

� Dynamic routing protocols are usuallyy a c ou g p o oco s a e usua yused in larger networks to ease the administrative and operational overhead f i l t ti tof using only static routes.

� Typically, a network uses a combination f b th d i ti t l dof both a dynamic routing protocol and

static routes.

3© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

The Evolution of Dynamic Routing Protocols

� One of the earliest routing protocols was Routing Information Protocol (RIP).RIP h l d i t i RIP 2 H–RIP has evolved into a newer version RIPv2. However,

–The newer version of RIP still does not scale to larger network implementations.

� To address the needs of larger networks, two advanced routing protocols were developed: Open Shortest Path First (OSPF) and Intermediate System-to-I t di t S t (IS IS)Intermediate System (IS-IS).

� Cisco developed Interior Gateway Routing Protocol (IGRP) and Enhanced IGRP (EIGRP), which also scales well in larger network implementations.

� Additionally there was the need to interconnect different internetworks and provide� Additionally, there was the need to interconnect different internetworks and providerouting among them. Border Gateway Routing (BGP) protocol is now used between ISPs as well as between ISPs and their larger private clients to exchange routing information.

� With the advent of numerous consumer devices using IP the IPv4 addressing space� With the advent of numerous consumer devices using IP, the IPv4 addressing spaceis nearly exhausted. Thus IPv6 has emerged. To support the communication based on IPv6, newer versions of the IP routing protocols have been developed (see the IPv6 row in the table).

4© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 85: Nota CCNA Exp 2 - Routing Protocols and Concepts

Dynamic Routing Protocols

� Function(s) of Dynamic Routing Protocols:-Dynamically share information between routers.-Automatically update routing table when topology changes.-Determine best path to a destinationDetermine best path to a destination.–Compared to static routing, dynamic routing protocols require less administrative overhead.

•However, the expense of using dynamic routing protocols is dedicating part of a router'sHowever, the expense of using dynamic routing protocols is dedicating part of a router sresources for protocol operation including CPU time and network link bandwidth.

– One of the primary benefits to using a dynamic routing protocol is that routers exchange routing information whenever there is a topology change. This exchange ll t t t ti ll l b t t k d l t fi d lt tallows routers to automatically learn about new networks and also to find alternate

paths when there is a link failure to a current network.

5© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Dynamic Routing Protocols

� Despite the benefits of dynamic routing, static routing stillesp e e be e s o dy a c ou g, s a c ou g shas its place.

� There are times when static routing is more appropriate andThere are times when static routing is more appropriate andother times when dynamic routing is the better choice.

� More often than not you will find a combination of bothMore often than not, you will find a combination of bothtypes of routing in any network that has a moderate level of complexity.

6© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 86: Nota CCNA Exp 2 - Routing Protocols and Concepts

Dynamic Routing Protocols

� A routing protocolg p–is a set of processes, algorithms, and messages that are used to exchange routing information and populate the routing table with the routing protocol's choice of best pathsg p p

� The purpose of a dynamic routing protocol is to:-Discover remote networks-Maintaining up-to-date routing information-Choosing the best path to destination networksAbilit t fi d b t th if th t th i l il bl-Ability to find a new best path if the current path is no longer available

7© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Dynamic Routing ProtocolsDynamic Routing Protocols� Components of a routing protocol

–Data structuresData structures•Some routing protocols use tables and/or databases for its operations. This information is kept in RAM

Al ith–Algorithm•Algorithm is a finite list of steps used in accomplishing a task•Algorithms are used for facilitating routing information and best pathAlgorithms are used for facilitating routing information and best pathdetermination

–Routing protocol messagesTh f di i i hb d h f•These are messages for discovering neighbors and exchange of

routing information , and other tasks to learn and maintain accurate information about the network.

8© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 87: Nota CCNA Exp 2 - Routing Protocols and Concepts

Dynamic Routing Protocol OperationDynamic Routing Protocol Operation� All routing protocols have the same purpose - to learn about remote networks

and to quickly adapt whenever there is a change in the topology.

� The method that a routing protocol uses to accomplish this depends upon the algorithm it uses and the operational characteristics of that protocol.

� In general the operations of a dynamic routing protocol can be described as� In general, the operations of a dynamic routing protocol can be described asfollows:

–The router sends and receives routing messages on its interfaces.–The router shares routing messages and routing information with other routers that are using the same routing protocol.–Routers exchange routing information to learn about remote networks. –When a router detects a topology change the routing protocol can advertise this change to other routers.

9© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Dynamic Routing Protocols

� Advantages of static routingIt b k lti l

� Advantages of dynamic routing-It can backup multipleinterfaces/networks on a router-Minimal CPU processingEasier for administrator to

-Administrator has less work maintaining the configuration when adding or deleting networks.

-Easier for administrator tounderstand-Easy to configure-No extra resources are needed

-Protocols automatically react to the topology changes.-Configuration is less error-prone.No extra resources are needed

-More secure� Disadvantages of static routing

g-More scalable, growing the network usually does not present a problem

� Disadvantages of dynamic routing-Network changes require manual reconfiguration-Configuration and maintenance is time-consuming

� Disadvantages of dynamic routing-Router resources are used (CPU cycles, memory and link bandwidth).

time consuming-Does not scale well in large topologies-Configuration is error-prone,

-More administrator knowledge is required for configuration, verification, and troubleshooting.

10© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

g p ,especially in large networks

Page 88: Nota CCNA Exp 2 - Routing Protocols and Concepts

Dynamic Routing Protocols

11© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Classifying Routing Protocols

� Dynamic routing protocols are grouped according to y g p g p gcharacteristics. Examples include:

-RIPIGRP-IGRP

-EIGRPOSPF-OSPF

-IS-IS-BGPBGP

� Autonomous System is a group of routers under the control of a single authority.

12© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 89: Nota CCNA Exp 2 - Routing Protocols and Concepts

Classifying Routing Protocols

� Dynamic routing protocols:–RIP

•A distance vector interior routing protocol–IGRP

•The distance vector interior routing developed by Cisco (deprecated from 12.2 IOS and later)

–EIGRP•The advanced distance vector interior routing protocol developed by Cisco

OSPF–OSPF•A link-state interior routing protocol

–IS-IS•A link-state interior routing protocol

–BGP•A path vector exterior routing protocol

13© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

p g p

Classifying Routing ProtocolsClassifying Routing Protocols� An autonomous system (AS) - otherwise known as a

routing domain - is a collection of routers under a common administration.common administration.

� Because the Internet is based on the ASs concept, two types of routing protocols are required: interior and exterior routing protocols.

Interior Gateway Protocols (IGP)-Interior Gateway Protocols (IGP)•are used for intra-autonomous system routing - routing inside an autonomous system•IGPs are used for routing within a routing domain, those networks within the control of a single organization.g g

–An autonomous system is commonly comprised of many individual networks belonging to companies, schools, and other institutions.

• IGPs for IP include RIP, IGRP, EIGRP, OSPF, and IS-ISExterior Gateway Protocols (EGP)-Exterior Gateway Protocols (EGP)

•are used for inter-autonomous system routing - routing between autonomous systems that are under the control of different administrations•At the ISP level, there are often more important issuesAt the ISP level, there are often more important issuesthan just choosing the fastest path. •BGP is typically used between ISPs and sometimes between a company and an ISP

14© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 90: Nota CCNA Exp 2 - Routing Protocols and Concepts

A t tAutonomous systems� An autonomous system (AS) is a collection of

networks under a common administrationnetworks under a common administrationsharing a common routing strategy.

To the outside world, an AS is viewed as a single entity. The AS may be run by one or more operators while presenting a consistent view of routing to the external world.

� The American Registry of Internet Numbers (ARIN), a service provider, or an administrator assigns an identifying number to each AS. This g y gautonomous system number is a 16 bit number.Routing protocols, such as Cisco’s IGRP, require assignment of a unique, autonomous system number.

American Registry for Internet Numbershttp://www.arin.net/registration/asn/index.html

A t S t b (ASN) id

15© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Autonomous System number (ASN) resource guidehttp://www.apnic.net/services/asn_guide.html

IS-IS

Autonomous systemsAutonomous systems� Cisco system AS number:

� http://ws.arin.net/cgi-bin/whois.pl

16© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 91: Nota CCNA Exp 2 - Routing Protocols and Concepts

Autonomous systemsAutonomous systems� http://arin.net/education/asn_process/index.html

RFC 1930� AS just like IP, it needs

to apply from ARIN or the appropriate region and be unique on the i t tinternet.

� The Internet Assigned Numbers Authority (IANA) has reserved the following block of AS numbers for private use (not to be advertised on the global Internet): 64512 through 65535

17© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Classifying Routing ProtocolsClassifying Routing Protocols� IGP: Comparison of Distance Vector & Link

State Routing ProtocolsDistance vector

– routes are advertised as vectors of distance & direction.

•Distance is defined in terms of a metric such as hop count (RIP)•Direction is simply the next-hop router or exit interfaceinterface•Distance vector protocols typically use the Bellman-Ford algorithm for the best path route determination

– incomplete view of network topologyincomplete view of network topology.•Distance vector protocols use routers as sign posts along the path to the final destination. •Distance vector routing protocols do not have an g pactual map of the network topology

– Generally, periodic updates.•Some distance vector protocols periodically send

18© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

complete routing tables to all connected neighbors.

Page 92: Nota CCNA Exp 2 - Routing Protocols and Concepts

Classifying Routing ProtocolsClassifying Routing Protocols� IGP: Comparison of Distance Vector &

Link State Routing ProtocolsLink State Routing ProtocolsLink state

– complete view of network topology is created.p p gy•The sign posts along the way from source to destination are not necessary, because all link-state routers are using an identical "map" of thestate routers are using an identical map of thenetwork.

– updates are not periodic.•After the network has converged, a link-state update only sent when there is a change in the topology.

19© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Classifying Routing ProtocolsClassifying Routing Protocols� Comparison of Distance Vector & Link State Routing Protocols

Di t t t l k� Distance vector protocols workbest in situations where:

–The network is simple and flat

� Link-state protocols work best in situations where:

–The network design is hierarchical,pand does not require a special hierarchical design.–The administrators do not have

g ,usually occurring in large networks.–The administrators have a good knowledge of the implemented link-

enough knowledge to configure and troubleshoot link-state protocols.

knowledge of the implemented linkstate routing protocol.–Fast convergence of the network is crucial

–Specific types of networks, such as hub-and-spoke networks, are being implemented.

crucial.

–Worst-case convergence times in a network are not a concern.

20© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 93: Nota CCNA Exp 2 - Routing Protocols and Concepts

Classifying Routing Protocols� Classful routing protocols

–Do NOT send subnet mask in routing updatesDo NOT send subnet mask in routing updates,–Do NOT support VLSM,–Classful routing protocols cannot be used when a network is subnetted using more than one gsubnet mask,

• Tony: This does not mean you can not subnet the clasasfull network. You can still subnet it but can only do it once and allsubnet it, but can only do it once and allnetwork needs to have the identical mask.

–Routing protocols such as RIPv1 and IGRP.

� Classless routing protocolsg p–Do send subnet mask in routing updates.–support variable length subnet masks (VLSM).

•In the figure, the classless version of the network is g ,using both /30 and /27 masks in the same topology. •Tony: It means you can create the network with all different sizes of subnets. They don’t need to have the same mask.

21© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

need to have the same mask.•Classless routing protocols are RIPv2, EIGRP, OSPF, IS-IS, BGP.

Classifying Routing Protocols

� Convergence is defined as when all routers’ routingCo e ge ce s de ed as e a ou e s ou gtables are at a state of consistency

– The network has converged when all routers have complete and faccurate information about the network

� Convergence time is the time it takes routers to sharei f ti l l t b t th d d t th i tiinformation, calculate best paths, and update their routingtables.R ti t l b t d b d� Routing protocols can be rated based on the speed to convergence; the faster the convergence, the better the routing

t lprotocol.–RIP and IGRP are slow to converge–EIGRP and OSPF are faster to converge.

22© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

EIGRP and OSPF are faster to converge.

Page 94: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Protocols Metrics

� To select the best path, the routing l b bl l dprotocol must be able to evaluate and

differentiate between the available paths. For this purpose a metric is used.

� Metric–A value used by a routing protocol to determine which routes are better than others.

� Each routing protocol uses its own metric. –RIP uses hop count,

•The hop count refers to the number of routersThe hop count refers to the number of routersa packet must cross to reach the destination network.•For R3 in the figure, network 172.16.3.0 is two hops or two routers awayhops, or two routers away.

–EIGRP uses a combination of bandwidth and delay,–OSPF uses bandwidth (cost).

23© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

OSPF uses bandwidth (cost).

Routing Protocols Metrics

� Metrics used in IP routing protocols–Bandwidth

•Influences path selection by preferring the path with the highest bandwidth

–CostCost•A value determined either by the IOS or by the network administrator to indicate preference for a route. Cost can represent a metric, a combination of metrics or a policy.

RIP

OSPFp y

–Delay•Considers the time a packet takes to traverse a path

Hop count

RIP

–Hop count•A simple metric that counts the number of routers a packet must traverse

–Load•Considers the traffic utilization of a certain link

–Reliability•Assesses the probability of a link failure, calculated from the interface error count or

24© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

calculated from the interface error count orprevious link failures

Page 95: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Protocols MetricsRouting Protocols Metrics� The Metric Field in the Routing Table

� Metric used for each routing protocol-RIP - hop count-IGRP & EIGRP - Bandwidth (used by default), Delay (used by default), Load,ReliabilityReliability-IS-IS & OSPF – Cost, Bandwidth(Cisco’s implementation)

� Refer to the example in the figure TheRefer to the example in the figure Therouters are using the RIP routing protocol.

–The metric associated with a certain t b b t i d i throute can be best viewed using the

show ip route command.–The metric value is the second value in the brackets for a routing table entry. –In the figure, R2 has a route to the 192.168.8.0/24 network that is 2 hops away.

•R 192 168 8 0/24 [120/2] via

25© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

R 192.168.8.0/24 [120/2] via192.168.4.1, 00:00:26, Serial0/0/1

Routing Protocols Metrics

� Load balancingoad ba a c g–when two or more routes to the same destination have identical metric values–This is the ability of a router to distribute packets among multiple same cost pathsp

Load balancing does notLoad balancing does notautomatically means the interfaces

will get use equally. R2 load balances traffic to PC5 over two equal cost paths.

??????

26© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 96: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Protocols Metrics

� Load balancing can be done eitheroad ba a c g ca be do e e eper packet or per destination.

–How a router actually load balances packets between the equal-cost paths is governed by the switching process.

R2 load balances traffic to PC5 over two equal cost paths.

Example

27© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

CRouter Paths: Equal Cost Load Balancing� To solve this dilemma, a router will use Equal Cost Load

Balancing This means the router sends packets over the multipleBalancing. This means the router sends packets over the multipleexit interfaces listed in the routing table.

–per-packet load balancing•( Process Switching)

–per-destination load balancing. •(Fast Switching)•(Fast Switching)

Router(config-if)# ip route-cache Router(config-if)#no ip route-cache

ping 10.0.0.1ping 10.0.0.2 ping 10.0.0.1ping 10.0.0.2

28© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 97: Nota CCNA Exp 2 - Routing Protocols and Concepts

Load balancing with RIPLoad balancing with RIPdebug ip packet

IP k t d b i i

per-packet load balancingIP packet debugging is on

GAD#

*Mar 1 19:10:29.646: IP: tableid=0, s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/1), routed via RIB

*Mar 1 19:10:29.646: IP: s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/1), g=192.168.13.2, len 60, forward

*Mar 1 19:10:30.654: IP: tableid=0, s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/0), routed via RIB

*Mar 1 19:10:30.654: IP: s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/0), g=192.168.15.2, len 60, forward

*Mar 1 19:10:31.654: IP: tableid=0, s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/1), routed via RIB

*Mar 1 19:10:31.654: IP: s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/1), g=192.168.13.2, len 60, forward

*Mar 1 19:10:32.218: IP: s=0.0.0.0 (FastEthernet0/0), d=255.255.255.255, len 604, rcvd 2

*Mar 1 19:10:32.654: IP: tableid=0, s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/0), routed via RIB

*Mar 1 19:10:32.654: IP: s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/0), g=192.168.15.2, len 60, forward

*Mar 1 19:10:33.654: IP: tableid=0, s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/1), routed via RIB

*Mar 1 19:10:33.654: IP: s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/1), g=192.168.13.2, len 60, forward

*Mar 1 19:10:34.654: IP: tableid=0, s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/0), routed via RIB

*Mar 1 19:10:34.654: IP: s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/0), g=192.168.15.2, len 60, forward

*Mar 1 19:10:35.654: IP: tableid=0, s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/1), routed via RIB

*Mar 1 19:10:35.654: IP: s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/1), g=192.168.13.2, len 60, forward

*Mar 1 19:10:35.974: IP: s=192.168.13.1 (local), d=255.255.255.255 (Serial0/1), len 72, sending broad/multicast

*Mar 1 19:10:36.654: IP: tableid=0, s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/0), routed via RIB

*Mar 1 19:10:36.654: IP: s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/0), g=192.168.15.2, len 60, forward

29© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

( ), ( ), g , ,

http://www.cisco.com/en/US/products/ps5763/products_configuration_guide_chapter09186a00802a1fae.html#wp1045020RIB:

Router(config-if)#no ip route-cache

Load balancing with RIPLoad balancing with RIPdebug ip packet

IP k d b i i

per-destination load balancingIP packet debugging is on

GAD#

*Mar 1 19:14:36.006: IP: tableid=0, s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/0), routed via RIB

*Mar 1 19:14:36.006: IP: s=192.168.14.2 (FastEthernet0/0), d=192.168.16.2 (Serial0/0), g=192.168.15.2, len 60, forward

*Mar 1 19:14:36.026: IP: tableid=0, s=192.168.16.2 (Serial0/1), d=192.168.14.2 (FastEthernet0/0), routed via RIB

*Mar 1 19:14:36.026: IP: s=192.168.16.2 (Serial0/1), d=192.168.14.2 (FastEthernet0/0), g=192.168.14.2, len 60, forward

*Mar 1 19:14:37.978: IP: s=0.0.0.0 (FastEthernet0/0), d=255.255.255.255, len 604, rcvd 2

*Mar 1 19:14:44.122: IP: s=0.0.0.0 (FastEthernet0/0), d=255.255.255.255, len 604, rcvd 2

*Mar 1 19:14:46.562: IP: s=192.168.14.1 (local), d=255.255.255.255 (FastEthernet0/0), len 92, sending broad/multicast

*Mar 1 19:14:47.278: IP: s=192.168.15.1 (local), d=255.255.255.255 (Serial0/0), len 72, sending broad/multicast

*Mar 1 19:14:50.266: IP: s=0.0.0.0 (FastEthernet0/0), d=255.255.255.255, len 604, rcvd 2

*Mar 1 19:14:51.958: IP: s=192.168.13.2 (Serial0/1), d=255.255.255.255, len 72, rcvd 2

*Mar 1 19:14:51.962: IP: s=192.168.15.2 (Serial0/0), d=255.255.255.255

Router(config-if)# ip route-cache

30© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negarahttp://www.cisco.com/en/US/products/ps5763/products_configuration_guide_chapter09186a00802a1fae.html#wp1045020RIB:

Page 98: Nota CCNA Exp 2 - Routing Protocols and Concepts

� Unequal Cost Load Balancing with EIGRP

� EIGRP Load Balancing E ti t l t l t

What is unequal cost load balancing?

Every routing protocol supports equal costpath load balancing. In addition to that, IGRP and EIGRP also support unequal cost path load balancing.

Use the variance command to instruct the router to include routes with a metric less than n times the minimum metric route for that destination, where n is the number specified by the variancecommand.Example: E-C-A: 20 * 2 = 40. Therefore, E-C-A and E-B-A will be used for load balancing. router eigrp 1

network x.x.x.x variance 2

31© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

variance 2

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a008009437d.shtml

Administrative Distance of a Route

� In fact, a router might learn of a , groute to the same network from more than one source.

For example a static route might have– For example, a static route might havebeen configured for the same network/subnet mask that was learned dynamically by a dynamic routingdynamically by a dynamic routingprotocol, such as RIP. The router must choose which route to install.

P f t i� Purpose of a metric–It’s a calculated value used to determine the best path to a destination

� Purpose of Administrative Distance–It’s a numeric value that specifies the

For equal cost routes to be installed they both must be static routes or they both must be RIP

32© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

preference of a particular route source. routes or they both must be RIProutes.

Page 99: Nota CCNA Exp 2 - Routing Protocols and Concepts

Administrative Distance of a Route

� Administrative distance is an integer value from 0 to 255.g

� The lower the value the more preferred the route source. –An administrative distance of 0 is the most preferred. –Only a directly connected network has an administrative distance of 0, which cannot be changed–An administrative distance of 255 means the router will not believeAn administrative distance of 255 means the router will not believethe source of that route and it will not be installed in the routing table.

33© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Administrative Distance of a RouteAdministrative Distance of a Route� Identifying the Administrative Distance (AD) in a routing

tabletableIt is the first number in the brackets in the routing table

•R2 is running both RIP and EIGRP routing protocols.•R2 has learned of the 192.168.6.0/24 route from R1 through EIGRP updates and from R3 throughR1 through EIGRP updates and from R3 throughRIP updates. •RIP has an administrative distance of 120, but EIGRP has a lower administrative distance of 90. S R2 dd th t l d i EIGRP t

This show ip rip database commandshows all RIP routes learned by R2,

h th t th RIP t i i t ll d i

34© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

•So, R2 adds the route learned using EIGRP tothe routing table and forwards all packets for the 192.168.6.0/24 network to router R1.

whether or not the RIP route is installed inthe routing table.

Page 100: Nota CCNA Exp 2 - Routing Protocols and Concepts

Administrative Distance of a RouteAdministrative Distance of a Route� The AD value can also

be verified with thebe verified with theshow ip protocols command.

35© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Administrative Distance of a Route

� Directly connected routesect y co ected outes-Immediately appear in the routing table as soon as the interface is configured

36© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 101: Nota CCNA Exp 2 - Routing Protocols and Concepts

Administrative Distance of a Route

� Directly connected routesyHave a default AD of 0

� Static RoutesAdministrative distance of a static route has a default value of 1

� A static route using either a next-hop IP address or an exit interface has a default AD value of 1interface has a default AD value of 1.

–However, the AD value is not listed in show ip route when you configure a static route with the exit interface specified. When a static

t i fi d ith it i t f th t t h th t kroute is configured with an exit interface, the output shows the networkas directly connected via that interface.

37© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Administrative Distance of a Route

38© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 102: Nota CCNA Exp 2 - Routing Protocols and Concepts

SummarySummary� Dynamic routing protocols fulfill the following functions

-Dynamically share information between routers-Dynamically share information between routers-Automatically update routing table when topology changes-Determine best path to a destination

� Routing protocols are grouped as either-Interior gateway protocols (IGP)Or-Exterior gateway protocols(EGP)

� Types of IGPs includeCl l ti t l th t l i l d b t k-Classless routing protocols - these protocols include subnet mask

in routing updates-Classful routing protocols - these protocols do not include subnet

k i ti d tmask in routing update

39© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

SummarySummary� Metrics are used by dynamic routing protocols to calculate the

best path to a destinationbest path to a destination.� Administrative distance is an integer value that is used to

indicate a router’s “trustworthiness”indicate a router s trustworthiness� Components of a routing table include:

-Route sourceRoute source-Administrative distance (The smaller the better)-Metric (The smaller the better)( )

40© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 103: Nota CCNA Exp 2 - Routing Protocols and Concepts

Distance Vector Routing Protocols

Chapter 4: Routing Protocols and Concepts

Modified by Hasimi Sallehudin

1© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Objectives

� Identify the characteristics of distance vector routing protocols.y g p

� Describe the network discovery process of distance vector routing protocols using Routing Information Protocol (RIP).

� Describe the processes to maintain accurate routing tables used by distance vector routing protocols.

Id tif th diti l di t ti l d l i th� Identify the conditions leading to a routing loop and explain theimplications for router performance.

� Recognize that distance vector routing protocols are in use todayRecognize that distance vector routing protocols are in use today

2© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 104: Nota CCNA Exp 2 - Routing Protocols and Concepts

Distance Vector Routing Protocols

� Dynamic routing protocols help the network administrator overcome the time-consuming and exacting process of configuring and maintaining static routesconsuming and exacting process of configuring and maintaining static routes.

� Examples of Distance Vector routing protocols:�Routing Information Protocol (RIP)

RFC 1058–RFC 1058.–Hop count is used as the metric for path selection. –If the hop count for a network is greater than 15, RIP cannot supply a route to that network.R ti d t b d t lti t 30 d b d f lt–Routing updates are broadcast or multicast every 30 seconds, by default.

�Interior Gateway Routing Protocol (IGRP)–proprietary protocol developed by Cisco. –Bandwidth, delay, load and reliability are used to create a composite metric.Bandwidth, delay, load and reliability are used to create a composite metric.–Routing updates are broadcast every 90 seconds, by default. –IGRP is the predecessor of EIGRP and is now obsolete.

�Enhanced Interior Gateway Routing Protocol (EIGRP)y g ( )–Cisco proprietary distance vector routing protocol. –It can perform unequal cost load balancing. –It uses Diffusing Update Algorithm (DUAL) to calculate the shortest path. –There are no periodic updates as with RIP and IGRP Routing updates are sent only

3© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

–There are no periodic updates as with RIP and IGRP. Routing updates are sent onlywhen there is a change in the topology.

Distance Vector Routing Protocols

� The Meaning of Distance Vector:The Meaning of Distance Vector:–A router using distance vector routing protocols knows 2 things:

�Distance to final destination�Distance to final destination�The distance or how far it is to the destination network

�Vector or direction traffic should be directed�Vector, or direction, traffic should be directed�The direction or interface in which packets should be forwarded

For example, in the figure, R1 knows that the distance to reach network 172.16.3.0/24 is 1 hop and that the direction is out the i t f S0/0/0 t d R2

4© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

interface S0/0/0 toward R2.

Page 105: Nota CCNA Exp 2 - Routing Protocols and Concepts

Distance Vector Routing ProtocolsDistance Vector Routing Protocols� Characteristics of Distance Vector routing protocols:

� Periodic updatesp•Periodic Updates sent at regular intervals (30 seconds for RIP). Even if the topology has not changed in several days,

� Neighbors�The router is only aware of the network addresses of its own interfaces and the remote network addresses it can reach through its neighbors. �It has no broader knowledge of the network topology

� Broadcast updates�Broadcast Updates are sent to 255.255.255.255. �Some distance vector routing protocols use multicast addresses instead of broadcast addressesaddresses instead of broadcast addresses.

� Entire routing table is included with routing update�Entire Routing Table Updates are sent, with some exceptions to be discussed later, periodically to allexceptions to be discussed later, periodically to allneighbors.�Neighbors receiving these updates must process the entire update to find pertinent information and discard the rest. �Some distance vector routing protocols like EIGRP do not

5© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

�Some distance vector routing protocols like EIGRP do notsend periodic routing table updates.

Distance Vector Routing ProtocolsDistance Vector Routing Protocols� Routing Protocol Algorithm:

Th l ith i d t l l t th b t th d th d–The algorithm is used to calculate the best paths and then sendthat information to the neighbors.–Different routing protocols use different algorithms to install routes g p gin the routing table, send updates to neighbors, and make path determination decisions.

6© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 106: Nota CCNA Exp 2 - Routing Protocols and Concepts

Distance Vector Routing ProtocolsRouting Protocol Characteristics

Criteria used to compare routing protocols includes–Criteria used to compare routing protocols includes�Time to convergence

�Time to convergence defines how quickly the routers in the network topology share routing information and reach a state of consistent knowledge. �The faster the convergence, the more preferable the protocol.

�Scalability�Scalability defines how large a network can become based on the routing protocol that is deployeddeployed.�The larger the network is, the more scalable the routing protocol needs to be.

�Resource usage�Resource usage includes the requirements of a routing protocol such as memory space,g q g p y p ,CPU utilization, and link bandwidth utilization. �Higher resource requirements necessitate more powerful hardware to support the routing protocol operation

�Classless (Use of VLSM) or Classful( )�Classless routing protocols include the subnet mask in the updates. �This feature supports the use of Variable Length Subnet Masking (VLSM) and better route summarization.

�Implementation & maintenance

7© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

�Implementation & maintenance�Implementation and maintenance describes the level of knowledge that is required for a network administrator to implement and maintain the network based on the routing protocol deployed.

Distance Vector Routing ProtocolsDistance Vector Routing Protocols

8© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 107: Nota CCNA Exp 2 - Routing Protocols and Concepts

Network Discovery

� Router initial start up (Cold Starts)

Cold Starts� Router initial start up (Cold Starts)

When a router cold starts or powers up, it knows nothing about the network topology. It does not even know that there are devices on the other end of its links. The only information that a router has is from its own saved configuration file stored in NVRAM.

Initial network discovery-Initial network discovery�Directly connected networks are initially placed in

routing tablerouting table

9© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Network Discovery I iti l E hNetwork Discovery� Initial Exchange of Routing Information

–If a routing protocol is configured then

Initial Exchange

If a routing protocol is configured then•Routers will exchange routing information•Initially, these updates only include information about their directly connected networks.

� Routing updates received from other routers–Router checks update for new information

•If there is new information:–Metric is updated–New information is stored in routing table

� After this first round of update exchanges, each t k b t th t d t k f th irouter knows about the connected networks of their

directly connected neighbors. � However, did you notice that R1 does not yet know

about 10 4 0 0 and that R3 does not yet know aboutabout 10.4.0.0 and that R3 does not yet know about10.1.0.0?

–Full knowledge and a converged network will not take place until there is another exchange of routing information

10© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

information.

Page 108: Nota CCNA Exp 2 - Routing Protocols and Concepts

Network DiscoveryNetwork Discovery� Next Update of Routing Information

At thi i t th t h k l d b t

Next Update

–At this point the routers have knowledge abouttheir own directly connected networks andabout the connected networks of their immediate neighborsimmediate neighbors.–Continuing the journey toward convergence, the routers exchange the next round of periodic updates Each router again checks the updatesupdates. Each router again checks the updatesfor new information.

� Routing updates received from other routers–Router checks update for new information

•If there is new information:–Metric is updated–New information is stored in routing table

11© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Network DiscoveryNetwork Discovery� Distance vector routing protocols

Split horizon

typically implement a technique known as split horizon.

–Split horizon prevents information from being sent out the same interface from which it wasinterface from which it wasreceived.

For example R2 would not send–For example, R2 would not sendan update out Serial 0/0/0 containing the network 10.1.0.0 gbecause R2 learned about that network through Serial 0/0/0.

12© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 109: Nota CCNA Exp 2 - Routing Protocols and Concepts

Network DiscoveryNetwork Discovery� Exchange of Routing Information Next Update

–Router convergence is reached when•All routing tables in the network contain the same network informationinformation,•[Tony]: The above statement is trying to tell you, the routing tables contains the same network information, BUT, each router has it’s own

i i f h i blvariation of the routing table.

–Routers continue to exchange routing information

-If no new information is found then Convergence isreached

13© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Network Discovery and convergence� The amount of time it takes for a network to converge isThe amount of time it takes for a network to converge is

directly proportional to the size of that network.

� Convergence must be reached before a network is considered completely operable

� Speed of achieving convergence consists of 2 interdependent categoriescategories

–How quickly the routers propagate a change in the topology in a routing update to its neighbors–The speed of calculating best path routes using the new routing information collected

45

For example: It takes five rounds of periodic update intervals before most of the branch routers in Regions 1 2 and 3

2

3

14© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

routers in Regions 1, 2, and 3learn about the new routes advertised by B2-R4.

1

Page 110: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table Maintenance

� Periodic Updates: RIPv1 & RIPv2� Periodic Updates: RIPv1 & RIPv2–These are time intervals in which a router sends out its entire routing table.

•RIPv1: updates are sent every 30 seconds as a broadcast (255.255.255.255) whether or not there has been a topology changechange•RIPv2: updates are sent every 30 seconds as a multicast (224.0.0.9) whether or not there has been a topology change

15© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing Table Maintenance

� Periodic Updates: distance vector protocols� Periodic Updates: distance vector protocolsemploy periodic updates to exchange routing information with their neighbors and to maintain up-information with their neighbors and to maintain up-to-date routing information in the routing table.

Failure of a link–Failure of a link–Introduction of a new link–Failure of a router–Change of link parameters

16© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 111: Nota CCNA Exp 2 - Routing Protocols and Concepts

R ti T bl M i tRouting Table Maintenance� RIP uses 4 timers

–Update timerp• interval is a route sends an update

–Invalid timer•If an update has not been received after 180 seconds (the default) the route is marked asseconds (the default), the route is marked asinvalid by setting the metric to 16. •The route is retained in the routing table until the flush timer expires.

–Holddown timer•This timer stabilizes routing information and helps prevent routing loops during periods when the topology is converging on new information.B d f lt th h ldd ti i t f 180•By default, the holddown timer is set for 180

seconds.–Flush timer

•By default, the flush timer is set for 240 seconds which is 60 seconds longer than theseconds, which is 60 seconds longer than theinvalid timer. •When the flush timer expires, the route is removed from the routing table.

17© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing Table Maintenance

� EIGRPEIGRP–Unlike other distance vector routing protocols, EIGRP does not send periodic updates. –Instead, EIGRP sends bounded updates about a , proute when a path changes or the metric for that route changes.

� EIGRP routing updates are –Partial updates

•Updates sent only when there is a change in topology that influences routing information

T i d b t l h–Triggered by topology changes–Bounded

•Propagation of partial updates are automatically bounded so that only those routers that need thebounded so that only those routers that need theinformation are updated

–Non periodic•Updates are not sent out on a regular basis.

18© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Updates are not sent out on a regular basis.

More details on how EIGRP operates will be presented in Chapter 9.

Page 112: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table MaintenanceRouting Table Maintenance� RIP Triggered Updates

–Routing table update that is sent immediately to adjacent routers in response to a routing change– The receiving routers in turn generate triggered updates– The receiving routers, in turn, generate triggered updatesthat notify their neighbors of the change.

� Conditions in which triggered updates are sentConditions in which triggered updates are sent–Interface changes state–Route becomes unreachable–Route is placed in routing table

19© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing Table MaintenanceRouting Table Maintenance

� RIP Triggered Updates (problems)problems

� RIP Triggered Updates (problems)–Using only triggered updates would be sufficient if there were a guarantee that the wave of updates would reach everywave of updates would reach everyappropriate router immediately.

� However, there are two problems with triggered updates:triggered updates:

–Packets containing the update message can be dropped or corrupted by some link in the networknetwork.–The triggered updates do not happen instantaneously. It is possible that a router that has not yet received the triggered update will y gg pissue a regular update at just the wrong time, causing the bad route to be reinserted in a neighbor that had already received the triggered update

20© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

triggered update.

Page 113: Nota CCNA Exp 2 - Routing Protocols and Concepts

Triggered Extensions to RIPTriggered Extensions to RIP

P i itProblems and Prerequisites

� Prerequisites–RIP must be enabled for this feature to function.function.–This feature runs on a point-to-point, serial interface only –Triggered extensions to IP RIP increase efficiency of RIP on point-to-point, serial interfaces.p ,

•interface serial 0 • ip rip triggered

http://cisco.com/en/US/docs/ios/12_0t/12_0t1/feature/guide/trigrip.html

21© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing Table MaintenanceRouting Table Maintenance� Random Jitter

Synchronized updatesSynchronized updatesA condition where multiple routers on multi access LAN segments transmit routing updates at the same time.P bl ith h i d d t�Problems with synchronized updates

-Bandwidth consumption-Packet collisions (with hubs and not with switches)Packet collisions (with hubs and not with switches)

�Solution to problems withsynchronized updates

- Used of random variable called RIP_JITTER

•A good reference is : Routing TCP/IP (Jeff Doyle) page 193-196. •Update timers : timer for periodic update

22© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Update timers : timer for periodic update(default 30s) - RIP_JITTER (random to prevent colision - 15% of the update timers)

Page 114: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table MaintenanceRouting Table Maintenance� Random Jitter•Figure 5 1 RIP adds a small random variable to the update timer•Figure 5.1. RIP adds a small random variable to the update timerat each reset to help avoid routing table synchronization. The RIP updates from Cisco routers vary from 25.5 to 30 seconds, as h i th d lt ti f th d tshown in the delta times of these updates.

Routing TCP/IP, Volume I (CCIE ProfessionalProfessionalDevelopment)

23© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

http://www.ubookcase.com/book/Cisco/Routing.TCP.IP.Volume.I.CCIE.Professional.Development/source/1578700418/ch05lev1sec1.html#ch05fig1

R ti LRouting Loops

� Routing loops areA condition in which aA condition in which apacket is continuously transmitted within a

i f tseries of routerswithout ever reaching its destination.its destination.

24© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 115: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Loops

� Routing loops may be caused by:-Incorrectly configured static routes-Incorrectly configured route redistribution-Slow convergenceIncorrectl config red discard ro tes-Incorrectly configured discard routes

� Routing loops can create the following issuesExcess use of bandwidth-Excess use of bandwidth

-CPU resources may be strained-Network convergence is degradedNetwork convergence is degraded-Routing updates may be lost or not processed in a timely manner

25© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing Loops

� Routing loops can eliminate–Defining a maximum metric to prevent count to infinityg p y–Holddown timers–Split horizon–Route poisoning or poison reverse–Triggered updates

� Note: The IP protocol has its own mechanism to prevent the possibility of a packet traversing the

( ) fnetwork endlessly. IP has a Time-to-Live (TTL) fieldand its value is decremented by 1 at each router.

If the TTL is zero the router drops the packet

26© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

–If the TTL is zero, the router drops the packet.

Page 116: Nota CCNA Exp 2 - Routing Protocols and Concepts

Preventing loops with Count to Infinity

C t t I fi it� Count to Infinity–It is a condition that exists when inaccurate routing

d t i th t i l t "i fi it " fupdates increase the metric value to "infinity" for a network that is no longer reachable.

This is a routing loop whereby packets bounce–This is a routing loop whereby packets bounceinfinitely around a network.

27© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Preventing loops by Setting a maximum� Setting a maximumg

� Distance Vector routing protocols set a specified metric value to indicate infinityy

Once a router “counts to infinity” it marks the route as unreachable

� RIP defines infinity as 16 hops - an "unreachable" metric.metric.

28© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 117: Nota CCNA Exp 2 - Routing Protocols and Concepts

P ti l ith h ldd tiPreventing loops with holddown timers� Holddown timers are used to prevent regularHolddown timers are used to prevent regular

update messages from inappropriately reinstating a route that may have gone bad.

H ldd ti ll t t t t h t-Holddown timers allow a router to not accept any changes to a route for a specified period of time.

- Do not appept the update when the route is flapping-Point of using holddown timers

�Allows routing updates to propagate through network with the most current informationthe most current information.

29© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

fHolddown timers work in the following way1. A router receives an update from a neighbor indicating that a network that previously

ibl i l iblwas accessible is now no longer accessible.

2. The router marks the network as possibly down and starts the holddown timer.

3. If an update with a better metric for that network is received from any neighboring router during the holddown period the network is reinstated and the holddown timerrouter during the holddown period, the network is reinstated and the holddown timeris removed.

4. If an update from any other neighbor is received during the holddown period with the same or worse metric for that network, that update is ignored. Thus, more time is allowed for the information about the change to be propagated.

5. Routers still forward packets to destination networks that are marked as possibly down. This allows the router to overcome any issues associated with intermittent connectivity. If the destination network truly is unavailable and the packets areconnectivity. If the destination network truly is unavailable and the packets areforwarded, black hole routing is created and lasts until the holddown timer expires.

30© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 118: Nota CCNA Exp 2 - Routing Protocols and Concepts

P ti l ith h ldd tiPreventing loops with holddown timers

31© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

P ti l ith Split HorizonPreventing loops with Split Horizon� The Split Horizon Rule is used to prevent routing loops

� Split Horizon rule:

A router should not advertise a network through theA router should not advertise a network through theinterface from which the update came.

Because of split horizon, R1 also does not advertisedoes not advertisethe information about network 10 4 0 0 back to

32© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

10.4.0.0 back toR2

Page 119: Nota CCNA Exp 2 - Routing Protocols and Concepts

Preventing loops with Route Poisoning

� Split horizon with Route� Split horizon with Routepoisoning

–Route poisoning is used toRoute poisoning is used tomark the route as unreachable in a routing update that is sent to otherupdate that is sent to otherrouters.–Unreachable is interpreted

t i th t i t t th 1616as a metric that is set to themaximum.–For RIP, a poisoned route

1616

, phas a metric of 16.

33© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Preventing loops with poison reverse

� Split horizon with poison� Split horizon with poisonreverse

–The rule states that once aThe rule states that once arouter learns of an unreachable route through an interface advertise it asinterface, advertise it asunreachable back through the same interface

P i i ifi–Poison reverse is a specificcircumstance that overrides split horizon. It occurs to

th t R3 i tensure that R3 is notsusceptible to incorrect updates about network 10 4 0 0

34© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

10.4.0.0.

Page 120: Nota CCNA Exp 2 - Routing Protocols and Concepts

Preventing loops with TTLPreventing loops with TTL� IP & TTL

P f th TTL fi ld–Purpose of the TTL field

The TTL field is found in an IP header and i d t t k t f dl lis used to prevent packets from endlesslytraveling on a network

H th TTL fi ld k� How the TTL field works

-TTL field contains a numeric value

The numeric value is decreased by one byevery router on the route to the destination.

If numeric value reaches 0 thenPacket is discarded.

35© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Preventing loops with TTLPreventing loops with TTL

36© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 121: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Protocols TodayRouting Protocols Today� Factors used to determine whether to use RIP or EIGRP

includeinclude-Network size-Compatibility between models of routersCo pat b ty bet ee ode s o oute s-Administrative knowledge

37© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing Protocols Today

� RIP�Features of RIP:�Features of RIP:

-Supports split horizon & split horizon with poison reversepoison reverse

-Capable of load balancing

-Easy to configure

-Works in a multi vendor router environmentWorks in a multi vendor router environment

38© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 122: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Protocols Today

� RIP V2F t f RIP�Features of RIP:

•Includes the subnet mask in the routing updates,making it a classless routing protocol.•Has authentication mechanism to secure routing t bl d ttable updates.•Supports variable length subnet mask (VLSM).•Uses multicast addresses instead of broadcast.•Supports manual route summarization.

39© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing Protocols Today

� EIGRP�Features of EIGRP:Features of EIGRP:

-Triggered updatesEIGRP h ll t l d t t bli h-EIGRP hello protocol used to establish

neighbor adjacenciesSupports VLSM & route summarization-Supports VLSM & route summarization

-Use of topology table to maintain all routes-Classless distance vector routing protocol-Cisco proprietary protocol

40© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 123: Nota CCNA Exp 2 - Routing Protocols and Concepts

Summary

� Characteristics of Distance Vector routing� Characteristics of Distance Vector routingprotocols

–Periodic updatesp–RIP routing updates include the entire routing table–Neighbors are defined as routers that share a link and are configured to use the same protocolconfigured to use the same protocol

� The network discovery process for D.V. routing protocolprotocol

–Directly connected routes are placed in routing table 1st

–If a routing protocol is configured then•Routers will exchange routing information

–Convergence is reached when all network routers have the t k i f ti

41© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

same network information

Summary

� D.V. routing protocols maintains routing tables byg p g y–RIP sending out periodic updates–RIP using 4 different timers to ensure information is accurate and convergence is achieved in a timely manner–EIGRP sending out triggered updates

� D.V. routing protocols may be prone to routing loops– routing loops are a condition in which packets continuously traverse a networktraverse a network–Mechanisms used to minimize routing loops include defining maximum hop count, holddown timers, split horizon, route poisoning and triggered updates

42© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 124: Nota CCNA Exp 2 - Routing Protocols and Concepts

SSummary� Conditions that can lead to routing loops includeg

–Incorrectly configured static routes–Incorrectly configured route redistribution–Slow convergence–Incorrectly configured discard routes

� How routing loops can impact network performance includes:

–Excess use of bandwidth–CPU resources may be strained

N t k i d d d–Network convergence is degraded–Routing updates may be lost or not processed

43© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Summary

� Routing Information Protocol (RIP)A distance vector protocol that has 2 versions

RIPv1 – a classful routing protocolRIPv2 - a classless routing protocol

� Enhanced Interior Gateway Routing Protocol (EIGRP)

–A distance vector routing protocols that has some features of link state routing protocols

A Cisco proprietary routing protocol–A Cisco proprietary routing protocol

44© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 125: Nota CCNA Exp 2 - Routing Protocols and Concepts

RIP version 1

Chapter 5: Routing Protocols and Concepts

Modified by Hasimi Sallehudin

1© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Objectives

� Describe the functions, characteristics, and operationesc be e u c o s, c a ac e s cs, a d ope a oof the RIPv1 protocol.

� Configure a device for using RIPv1.Configure a device for using RIPv1.

� Verify proper RIPv1 operation.

f� Describe how RIPv1 performs automatic summarization.

� Configure, verify, and troubleshoot default routes propagated in a routed network implementing RIPv1.

� Use recommended techniques to solve problems related to RIPv1

2© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 126: Nota CCNA Exp 2 - Routing Protocols and Concepts

RIP Historical Impact

� RIP evolved from an earlier protocolpdeveloped at Xerox, called Gateway Information Protocol (GWINFO).

� With the development of Xerox Network System (XNS) GWINFO evolved intoSystem (XNS), GWINFO evolved intoRIP.

� It later gained popularity because it was implemented in the Berkeley Software p yDistribution (BSD) as a daemon named routed (pronounced "route-dee", not "rout-ed").

� Recognizing the need for standardization� Recognizing the need for standardizationof the protocol, Charles Hedrick wrote RFC 1058 in 1988, in which he documented the existing protocol and specified some improvementsspecified some improvements.

� Since then, RIP has been improved with RIPv2 in 1994 and with RIPng in 1997. IPv6 form of RIP called

RIPng (next generation) is

3© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

RIPng (next generation) isnow available

RIPv1

� RIP Characteristics–A classful, Distance Vector (DV) routing protocol(DV) routing protocol–Metric = hop count–Routes with a hop count > 15 pare unreachable–Updates are broadcast every 30 seconds30 seconds–The data portion of a RIP message is encapsulated into a UDP segment with botha UDP segment, with bothsource and destination port numbers set to 520.

4© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 127: Nota CCNA Exp 2 - Routing Protocols and Concepts

RIPv1RIPv1� RIP Message Format� RIP header - divided into 3 fieldsRIP header divided into 3 fields

–Command field•REQUEST (1)- Request either a partial or full table update from another RIP router.•RESPONSE (2) - A response to a request.

–Version field•1 or 2•1 or 2

–Must be zero•Must be zero" fields provide room for future expansion of the pprotocol.

� Route Entry - composed of 3 fields

–Address family identifier•CLNS, IPX, IP etc.

–IP address

5© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

–Metric

RIPv1

� RIP Operation–RIP uses 2 message types:

�Request message

-This is sent out on startup by each RIP-This is sent out on startup by each RIPenabled interface

Requests all RIP enabled neighbors to send-Requests all RIP enabled neighbors to sendrouting table

�Response messageResponse message

-Message sent to requesting router containing routing table

6© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

containing routing table

Page 128: Nota CCNA Exp 2 - Routing Protocols and Concepts

RIP 1RIPv1� IP addresses initially divided y

into classes

-Class AClass A

-Class B

C C-Class C

� RIP is a classful routing protocol

-Does not send subnet masks in routing updates

7© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Common RIP configuration issues g

RIP and IGRP:

� Classful network statements only

� IOS will take subnetted networks but will translate it into the classful network for the running-config.

8© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 129: Nota CCNA Exp 2 - Routing Protocols and Concepts

RIPv1RIPv1� Administrative Distance

–RIP’s default administrative distance is 120

9© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Basic RIPv1 Configuration

� A typical topology suitable forA typical topology suitable foruse by RIPv1 includes:

-Three router set upThree router set up-No PCs attached to LANs

U f 5 diff t IP-Use of 5 different IPsubnets

10© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 130: Nota CCNA Exp 2 - Routing Protocols and Concepts

B i RIP 1 C fi tiBasic RIPv1 Configuration� Router RIP CommandRouter RIP Command

–To enable RIP enter:Router rip at the global configuration prompt-Router rip at the global configuration prompt-Prompt will look like R1(config-router)#

11© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Basic RIPv1 ConfigurationBasic RIPv1 Configuration� Specifying Networksp y g

–Use the networkcommand to:

-Enable RIP on all interfaces that belong to this network-Advertise this network in RIP updatesupdatessent to other routers

12© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

every 30 seconds

Page 131: Nota CCNA Exp 2 - Routing Protocols and Concepts

Verification and Troubleshooting

� Show ip Route

� To verify and� To verify andtroubleshoot routing

-Use the following

commands:

-show ip route

show ip protocols-show ip protocols

-debug ip rip

13© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

V ifi ti d T bl h tiVerification and Troubleshooting

� show ip protocols� show ip protocolscommand

-Displaysrouting

t lprotocolconfigured

ton router

POP QUIZ:POP QUIZ:What is the different

between the output of the command “show ip route”

14© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

pand “show ip protocol”?

Page 132: Nota CCNA Exp 2 - Routing Protocols and Concepts

Verification and TroubleshootingVerification and Troubleshooting� Debug ip rip command

Used to display RIP routing updates as they are-Used to display RIP routing updates as they arehappening

15© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Verification and Troubleshooting

� Passive interface command

-Used to prevent a router from sending updates throughUsed to prevent a router from sending updates throughan interface

-Example:-Example:

Router(config-router)#passive-interface interface-type interface-number

16© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 133: Nota CCNA Exp 2 - Routing Protocols and Concepts

Verification and Troubleshooting

� Passive interfacesPassive interfaces

17© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Preventing routing updates through an interface g g p g� Route filtering works by regulating the

routes that are entered into or advertised out of a route table.

L bAs a result, a route filter influences which routes the router advertises to its neighbors.

� On the other hand routers running link

Lab:

� On the other hand, routers running linkstate protocols determine routes based on information in the link-state database. Route filters have no effect on link-state advertisements or the link state databaseadvertisements or the link-state database.

(Tony) Route filtering could have negative effect on the link-state routing protocol.

� Using the passive interface command� Using the passive interface commandcan prevent routers from sending routing updates through a router interface, butthe router continues to listen and use routing updates from that neighborrouting updates from that neighbor.

Keeping routing update messages from being sent through a router interface prevents other systems on that network from learning about routes dynamically

18© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

from learning about routes dynamically.

Page 134: Nota CCNA Exp 2 - Routing Protocols and Concepts

Preventing routing updatesPreventing routing updatesthrough an interface

� Again this is only half the

It will break the rip update1

� Again, this is only half thestory.

When you use “passiveWhen you use “passiveinterface” on a distance vector routing protocol, youg p , yneed to complement it with “ip route” command.

You can use the “ip route”command to send route update

b k bli h h 22

back to establish the 2 way communication

19© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Automatic SummarizationAutomatic SummarizationModified Topology� The original scenario has beenThe original scenario has been

modified such that:Three classful networks are used:

172.30.3.0

172.30.0.0/16192.168.4.0/24192 168 5 0/24

172.30.2.0

172.30.1.0

192.168.5.0/24The 172.30.0.0/16 network is subnetted into three subnets:

172.30.1.0/24172.30.2.0/24172.30.3.0/24

The following devices are part of the 172.30.0.0/16 classful network address:

20© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

All interfaces on R1S0/0/0 and Fa0/0 on R2

Page 135: Nota CCNA Exp 2 - Routing Protocols and Concepts

Automatic Summarization

C fi ti D t il� Configuration Details

-To remove the RIP routing th f ll iprocess use the following

command

N t iNo router rip

-To check the configuration use the following command

Show run

21© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Automatic SummarizationAutomatic Summarization� Boundary Routers

RIP automatically summarizes classful networks–RIP automatically summarizes classful networks–Boundary routers summarize RIP subnets from one major network to anothermajor network to another.

22© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 136: Nota CCNA Exp 2 - Routing Protocols and Concepts

Automatic SummarizationAutomatic SummarizationProcessing RIP Updates� 2 rules govern RIPv1 updates:

-If a routing update and the interface it’s g preceived on belong to the samenetwork then

The subnet mask of theThe subnet mask of theinterface is applied to the network in the routing update

If a routing update and the interface it’s-If a routing update and the interface it sreceived on belong to a differentnetwork then

Th l f l b k f hThe classful subnet mask of thenetwork is applied to the network in the routing update.

23© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Automatic Summarization

� Sending RIP Updates� Sending RIP Updates–RIP uses automatic summarization to reduce the size of a routing tablesize of a routing table.

24© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 137: Nota CCNA Exp 2 - Routing Protocols and Concepts

A i S i iAutomatic Summarization� Advantages of automaticAdvantages of automatic

summarization:

-The size of-The size ofrouting updates is reduced

-Single routes are used to represent multiple routes which results in faster lookup in thefaster lookup in therouting table.

25© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Automatic SummarizationAutomatic Summarization� Disadvantage of Automatic Summarization:

-Does not support discontiguous networks

26© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 138: Nota CCNA Exp 2 - Routing Protocols and Concepts

Automatic Summarization

� DiscontiguousTopologies do not

i h RIP 1converge with RIPv1

� A router will onlyA router will onlyadvertise major network addresses out interfaces that do not belong to the advertised route.

27© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Automatic Summarization

28© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 139: Nota CCNA Exp 2 - Routing Protocols and Concepts

Default Route and RIPv1Default Route and RIPv1� Modified Topology: Scenario Cp gy

� Default routes P k h d fi d ifi ll i iPackets that are not defined specifically in a routingtable will go to the specified interface for the default routeroute

Example: Customer routers use default routes to connect to an ISP router.connect to an ISP router.

Command used to configure a default route isip route 0 0 0 0 0 0 0 0 s0/0/1ip route 0.0.0.0 0.0.0.0 s0/0/1

29© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Default Route and RIPv1Default Route and RIPv1

30© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 140: Nota CCNA Exp 2 - Routing Protocols and Concepts

D f lt R t d RIP 1Default Route and RIPv1� Propagating the Default Route in RIPv1Propagating the Default Route in RIPv1

� Default-information originate commandThis command is used to specify that the router is to originate-This command is used to specify that the router is to originate

default information, by propagating the static default route in RIP update.

31© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Default route with RIP

Centre#show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile,

Gateway of last resort is not set M bil # h i tGateway of last resort is not set

R 192.168.4.0/24 [120/1] via 192.168.2.1, 00:00:11, Serial0R 192.168.1.0/24 [120/1] via 192.168.2.1, 00:00:11, Serial0C 192.168.2.0/24 is directly connected, Serial0

Mobile#sho ip route

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile,

Gateway of last resort is not set

R 192 168 4 0/24 [120/1] i 192 168 1 1 00 00 04 S i l0C 192.168.3.0/24 is directly connected, Ethernet0 R 192.168.4.0/24 [120/1] via 192.168.1.1, 00:00:04, Serial0

C 192.168.5.0/24 is directly connected, Ethernet0

C 192.168.1.0/24 is directly connected, Serial0

R 192.168.2.0/24 [120/1] via 192.168.1.1, 00:00:04, Serial0

R 192 168 3 0/24 [120/2] via 192 168 1 1 00:00:04 Serial0

Centre(config)#ip route 0.0.0.0 0.0.0.0 loopback0Setup up a default route on the Centre router

Centre(config)#router rip R 192.168.3.0/24 [120/2] via 192.168.1.1, 00:00:04, Serial0Centre(config)#router ripCentre(config-router)#default-information originate

Centre#sh ip route

Codes: C - connected, S - static, * - candidate default

Mobile#sho ip route

Codes: C - connected, S - static, * - candidate default - RIP, , ,

Gateway of last resort is 0.0.0.0 to network 0.0.0.0

C 172.16.1.1 is directly connected, Loopback0

R 192.168.4.0/24 [100/8576] via 192.168.2.1, 00:00:22, Serial0

Gateway of last resort is 192.168.1.1 to network 0.0.0.0

R 192.168.4.0/24 [120/1] via 192.168.1.1, 00:00:09, Serial0

C 192.168.5.0/24 is directly connected, Ethernet0

32© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

9 68 0/ [ 00/85 6] a 9 68 , 00 00 , Se a 0

R 192.168.5.0/24 [120/2] via 192.168.2.1, 00:00:22, Serial0

S* 0.0.0.0/0 is directly connected, Loopback0

C 192.168.1.0/24 is directly connected, Serial0

R 192.168.2.0/24 [120/1] via 192.168.1.1, 00:00:04, Serial0

R 192.168.3.0/24 [120/2] via 192.168.1.1, 00:00:09, Serial0

R* 0.0.0.0/0 [120/2] via 192.168.1.1, 00:00:09, Serial0

Page 141: Nota CCNA Exp 2 - Routing Protocols and Concepts

Summary

� RIP characteristics include:

Cl f l di t t ti t lClassful, distance vector routing protocol

Metric is Hop Count

Does not support VLSM or discontiguous subnets

Updates every 30 secondsUpdates every 30 seconds

� Rip messages are encapsulated in a UDP segment with source and destination ports of 520with source and destination ports of 520

33© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Summary: Commands used by RIPCommand Command’s purpose

Rtr(config)#router rip Enables RIP routing process

Rtr(config-router)#network Associates a network with a RIP routing process

Rtr#debug ip rip used to view real time RIP routing updates

Rtr(config-router)#passive-interface fa0/0 Prevent RIP updates from going out an interface

Rtr(config-router)#default-information originate Used by RIP to propagate default routes

Rtr#show ip protocols Used to display timers used by RIP

34© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

p p p y y

Page 142: Nota CCNA Exp 2 - Routing Protocols and Concepts

VLSM and CIDR

Chapter 6: Routing Protocols and Concepts

Modified by Hasimi Sallehudin

1© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Objectives

� Compare and contrast classful and classless IP Co pa e a d co as c ass u a d c ass essaddressing.

� Review VLSM and explain the benefits of classless IPReview VLSM and explain the benefits of classless IPaddressing.

� Describe the role of the Classless Inter-DomainDescribe the role of the Classless Inter DomainRouting (CIDR) standard in making efficient use of scarce IPv4 addresses

� In addition to subnetting, it became possible to summarize a large collection of classful networks into an aggregate route, or supernet.

2© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 143: Nota CCNA Exp 2 - Routing Protocols and Concepts

IntroductionIntroduction� Prior to 1981, IP addresses used only the first 8 bits to specify the

network portion of the addressp

� In 1981, RFC 791 modified the IPv4 32-bit address to allow for three different classes

•Class A addresses used 8 bits for the network portion of the address, •Class B used 16 bits, •Class C used 24 bits•Class C used 24 bits.

–This format became known as classful IP addressing.

� IP address space was depleting rapidlyIP address space was depleting rapidlythe Internet Engineering Task Force (IETF) introduced ClasslessInter-Domain Routing (CIDR)

–CIDR uses Variable Length Subnet Masking (VLSM) to help conserve address space.

-VLSM is simply subnetting a subnet

3© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

-VLSM is simply subnetting a subnet

IntroductionIntroduction� With the introduction of CIDR and VLSM, ISPs

co ld no assign one part of a classf l net ork tocould now assign one part of a classful network toone customer and different part to another customercustomer.

� This discontiguous address assignment by ISPs was paralleled by the development of classless routing protocols.

–Classless routing protocols do include the subnet mask in routing updates and are not required to perform

i tisummarization.–The classless routing protocols discussed in this course are RIPv2 EIGRP and OSPF

4© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

course are RIPv2, EIGRP and OSPF.

Page 144: Nota CCNA Exp 2 - Routing Protocols and Concepts

Classful and Classless IP AddressingClassful and Classless IP Addressing� Classful IP addressing

When the ARPANET was commissioned in 1969 no one–When the ARPANET was commissioned in 1969, no oneanticipated that the Internet would explode. –1989, ARPANET transformed into what we now call the Internet.

As of January 2007 there are over 433 million hosts on internet–As of January 2007, there are over 433 million hosts on internet

� Initiatives to conserve IPv4 address space include:VLSM & CIDR notation (1993 RFC 1519)-VLSM & CIDR notation (1993, RFC 1519)

-Network Address Translation (1994, RFC 1631)Private Addressing (1996 RFC 1918)-Private Addressing (1996, RFC 1918)

5© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Classful and Classless IP AddressingClassful and Classless IP Addressing� Classes of IP addresses are identified by the decimal number

of the 1st octetClass A address begin with a 0 bit

Range of class A addresses = 0 0 0 0 to 127 255 255 255Range of class A addresses 0.0.0.0 to 127.255.255.255

Class B address begin with a 1 bit and a 0 bit

Range of class B addresses = 128 0 0 0 to 191 255 255 255Range of class B addresses = 128.0.0.0 to 191.255.255.255

Class C addresses begin with two 1 bits & a 0 bit

R f l C dd 192 0 0 0 t 223 255 255 255Range of class C addresses = 192.0.0.0 to 223.255.255.255.

6© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 145: Nota CCNA Exp 2 - Routing Protocols and Concepts

Classful and Classless IP AddressingClassful and Classless IP Addressing� Multicast addresses begin with three 1s and a 0 bit.g

Multicast addresses are used to identify a group of hosts that are part of a multicast group.

� IP addresses that begin with four 1 bits were reserved for future use.

7© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Classf l and Classless IP AddressingClassful and Classless IP Addressing� The IPv4 Classful Addressing Structure (RFC 790)

A IP dd h 2An IP address has 2 parts:

-The network portion

Found on the left side of an IP address

-The host portion

Found on the right side of an IP address

8© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 146: Nota CCNA Exp 2 - Routing Protocols and Concepts

Classf l and Classless IP AddressingClassful and Classless IP Addressing� As shown in the figure, class A networks used the first octet

for network assignment which translated to a 255 0 0 0for network assignment, which translated to a 255.0.0.0classful subnet mask.

–Because only 7 bits were left in the first octet (remember the first bitBecause only 7 bits were left in the first octet (remember, the first bitis always 0), this made 2 to the 7th power or 128 networks. –With 24 bits in the host portion, each class A address had the

t ti l f 16 illi i di id l h t ddpotential for over 16 million individual host addresses.

9© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Classf l and Classless IP AddressingClassful and Classless IP Addressing� With 24 bits in the host portion, each class A address had

the potential for over 16 million individual host addressesthe potential for over 16 million individual host addresses.� What was one organization going to do with 16 million

addresses?addresses?� Now you can understand the tremendous waste of address

space that occurred in the beginning days of the Internet, p g g ywhen companies received class A addresses.

� Some companies and governmental organizations still have l A ddclass A addresses.

–General Electric owns 3.0.0.0/8, Apple Computer owns 17 0 0 0/8–Apple Computer owns 17.0.0.0/8,

–U.S. Postal Service owns 56.0.0.0/8.

10© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 147: Nota CCNA Exp 2 - Routing Protocols and Concepts

Classf l and Classless IP AddressingClassful and Classless IP Addressing� Class B: RFC 790 specified the first two octets as

networknetwork.–With the first two bits already established as 1 and 0, 14 bits remained in the first two octets for assigning networks, which resulted in 16 384 class B network addressesresulted in 16,384 class B network addresses.–Because each class B network address contained 16 bits in the host portion, it controlled 65,534 addresses. (Remember, 2 addresses were reserved for the network and broadcastaddresses were reserved for the network and broadcastaddresses.)

11© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Classf l and Classless IP AddressingClassful and Classless IP Addressing� class C: RFC 790 specified the first three octets

as networkas network.–With the first three bits established as 1 and 1 and 0, 21 bits remained for assigning networks for over 221 bits remained for assigning networks for over 2million class C networks.–But, each class C network only had 8 bits in the host yportion, or 254 possible host addresses.

12© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 148: Nota CCNA Exp 2 - Routing Protocols and Concepts

Classf l and Classless IP AddressingClassful and Classless IP Addressing� Classful Routing Updates

–Recall that classful routing protocols (i.e. RIPv1) do not send subnet masks in their routing updates –This is because the router receiving the routing update could–This is because the router receiving the routing update coulddetermine the subnet mask simply by examining the value of the first octet in the network address, or by applying its ingress interface mask for subnetted routes The subnet mask wasinterface mask for subnetted routes. The subnet mask wasdirectly related to the network address.

/24 /16

13© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

/24

Classf l and Classless IP AddressingClassful and Classless IP Addressing� In the example,

R1 knows that subnet 172 16 1 0 belongs to the same major classful–R1 knows that subnet 172.16.1.0 belongs to the same major classfulnetwork as the outgoing interface. Therefore, it sends a RIP update to R2 containing subnet 172.16.1.0.

When R2 recei es the pdate it applies the recei ing interface s bnet•When R2 receives the update, it applies the receiving interface subnetmask (/24) to the update and adds 172.16.1.0 to the routing table

–When sending updates to R3, R2 summarizes subnets 172.16.1.0/24, 172 16 2 0/24 d 172 16 3 0/24 i t th j l f l t k 172 16 0 0172.16.2.0/24, and 172.16.3.0/24 into the major classful network 172.16.0.0.

•Because R3 does not have any subnets that belong to 172.16.0.0, it will apply the classful mask for a class B network, /16

/16

14© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

/24 /16

Page 149: Nota CCNA Exp 2 - Routing Protocols and Concepts

Classful and Classless IP Addressing� Classless Inter-domain Routing (CIDR – RFC 1517)g ( )

�Advantage of CIDR :�More efficient use of IPv4 address space�Route summarization

�(� reduce routing table size)�(� reduce routing update traffic)�(� reduce routing update traffic)

�Requires subnet mask to be included in routing update because address class is meaningless

� The network portion of the address is determined by the network subnet mask, also known as the network prefix, or prefix length (/8, /19, etc.). �The network address is no longer determined by the class of the address�Blocks of IP addresses could be assigned to a network based on the

15© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Blocks of IP addresses could be assigned to a network based on therequirements of the customer, ranging from a few hosts to hundreds or thousands of hosts.

Classful and Classless IP AddressingClassful and Classless IP Addressing� Classless IP Addressing

� CIDR & Route Summarization–Variable Length Subnet Masking (VLSM)–Allows a subnet to be further sub-netted

•according to individual needs–Prefix Aggregation a.k.a. Route Summarization–CIDR allows for routes to be summarized as a single route

16© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 150: Nota CCNA Exp 2 - Routing Protocols and Concepts

Classful and Classless IP AddressingClassful and Classless IP Addressing� Route Summarization

– In the figure, notice that ISP1 has four customers, each with a variable amount of IP address space.

However all of the customer address space can be summarized–However, all of the customer address space can be summarizedinto one advertisement to ISP2. –The 192.168.0.0/20 summarized or aggregated route includes all the networks belonging to Customers A, B, C, and D.

•This type of route is known as a supernet route. A t i lti l t k dd ith k•A supernet summarizes multiple network addresses with a mask

less than the classful mask.

17© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Classful and Classless IP AddressingClassful and Classless IP Addressing� Route Summarization

– Propagating VLSM and supernet routes requires a classless routing protocol, because the subnet mask can no longer be determined by the value of the first octet.

•Classless routing protocols include the subnet mask ith th t k dd i th ti d twith the network address in the routing update.

•RIPv2, EIGRP, IS-IS, OSPF and BGP. I i•Interior:

•RIPv2•EIGRPEIGRP•IS-IS•OSPF

Exterior:

18© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

•Exterior:•BGP

Page 151: Nota CCNA Exp 2 - Routing Protocols and Concepts

Classful and Classless IP AddressingClassful and Classless IP Addressing

�Is there any difference�Is there any differencebetween the terms CIDR and VLSM??

19© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Classful and Classless IP Addressing

� For example, the networks 172.16.0.0/16, 172.17.0.0/16, 172.18.0.0/16 pand 172.19.0.0/16 can be summarized as 172.16.0.0/14.

–If R2 sends the 172.16.0.0 summary route without the /14 mask, R3 only knows to apply the default classful mask of /16. –In a classful routing protocol scenario, R3 is unaware of the 172.17.0.0/16, 172.18.0.0/16 and 172.19.0.0/16 networks–With a classless routing protocol, R2 will advertise the 172.16.0.0g pnetwork along with the /14 mask to R3. R3 will then be able to install the supernet route 172.16.0.0/14 in its routing table giving it reachability to the 172.16.0.0/16, 172.17.0.0/16, 172.18.0.0/16 and 172.19.0.0/16 networks.

20© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

172.16.0.0 /14

Page 152: Nota CCNA Exp 2 - Routing Protocols and Concepts

Classful and Classless IP Addressing

Classless Routing Protocol� Classless Routing Protocol

Routing Routing Supports Ability toRoutingProtocol

RoutingupdatesInclude

SupportsVLSM

Ability tosend

Supernetc udesubnetMask

Supe eroutes

Classful

(RIPv1)No No No

(RIPv1)

Classless Yes Yes Yes

21© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

VLSMVLSM� Classful routing

only allows for one-only allows for onesubnet mask for all networks

� VLSM & classless routing-This is the processThis is the processof subnetting a subnet-More than one subnet mask can be used

-More efficient use of IP addresses as compared to classful IP

22© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

to classful IPaddressing

Page 153: Nota CCNA Exp 2 - Routing Protocols and Concepts

VLSMVLSM� VLSM – the process of

sub netting a subnet to fitsub-netting a subnet to fityour needs-Example:Example:Subnet 10.1.0.0/16, 8 more bits are borrowedo e b ts a e bo o edagain, to create 256 subnets with a /24 mask.

M k ll f 254 h t-Mask allows for 254 host addresses per subnet-Subnets range from: 10 1 0 0 / 24 t10.1.0.0 / 24 to10.1.255.0 / 24

* Same process for Subnet

23© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Same process for Subnet10.2.0.0/16

VLSMVLSM� Subnet 10.3.0.0/16, 12

more bits are borrowedmore bits are borrowedagain, to create 4,096 subnets with a /28 mask.

–Mask allows for 14 host addresses per subnet–Subnets range from: 10.3.0.0Subnets range from: 10.3.0.0/ 28 to 10.3.255.240 / 28

� Subnet 10.4.0.0/16, 4 more bit b d i tbits are borrowed again, tocreate 16 subnets with a /20 mask.

–Mask allows for 2,046 host addresses per subnetSubnets range from: 10 4 0 0

24© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

–Subnets range from: 10.4.0.0/ 20 to 10.4.240.0 / 20

Page 154: Nota CCNA Exp 2 - Routing Protocols and Concepts

Classless Inter Domain Routing (CIDR)Classless Inter-Domain Routing (CIDR)� Route summarization done by CIDR

-Routes are summarized with masks that are lessthan that of the default classful mask (supernetting)

-Example:

172.16.0.0 / 13 is the summarizedroute for the 172.16.0.0 / 16 to172.23.0.0 / 16 classful networks

Although 172.22.0.0/16 and 172.23.0.0/16 are not shown in the graphic, these are also included in the summary routeincluded in the summary route.

25© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Classless Inter Domain Routing (CIDR)Classless Inter-Domain Routing (CIDR)� Note: You may recall that a supernet is always a route summary, but

a route summary is not always a supernet.a route summary is not always a supernet.–It is possible that a router could have both a specific route entry and a summary route entry covering the same network.

L t th t t X h ifi t f 172 22 0 0/16 i–Let us assume that router X has a specific route for 172.22.0.0/16 usingSerial 0/0/1 and a summary route of 172.16.0.0/13 using Serial0/0/0. –Packets with the IP address of 172.22.n.n match both route entries. –These packets destined for 172.22.0.0 would be sent out the Serial0/0/1 interface because there is a more specific match of 16 bits, than with the 13 bits of the 172.16.0.0/13 summary route.

ip route 172.22.0.0 255.255.0.0 s 0/0/1

Router X

255.255.0.0 s 0/0/1

s 0/0/1

26© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 155: Nota CCNA Exp 2 - Routing Protocols and Concepts

Classless Inter-Domain Routing (CIDR)

� Steps to calculate a route summary

1 Li t t k i bi1. List networks in binaryformat2 Count number of left2. Count number of leftmost matching bits to determine summary

t ’ kroute’s mask3. Copy the matching bits and add zero bitsbits and add zero bitsto determine the summarized

27© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

network address

Example: Calculating a summary route

� Which address can be used� Which address can be usedto summarize networks

� A:• 192.168.0.0/30• 192.168.0.4/30

192 168 0 8/30

� 11000000 10101000 00000000 00000000� 11000000 10101000 00000000 00000100� 11000000 10101000 00000000 00001000• 192.168.0.8/30

• 192.168.0.16/29• B

� 11000000 10101000 00000000 00001000� 11000000 10101000 00000000 00010000

• 192.168.4.0/30• 192.168.5.0/30• 192 168 6 0/30

� 11000000 10101000 00000100 00000000� 11000000 10101000 00000101 00000000� 11000000 10101000 00000110 00000000• 192.168.6.0/30

• 192.168.7.0/29� 11000000 10101000 00000110 00000000� 11000000 10101000 00000111 00000000

Answer:28© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

� Answer:

Page 156: Nota CCNA Exp 2 - Routing Protocols and Concepts

Example: Calculating a summary route

� Reverse process of summary route:� Reverse process of summary route:� Can you figure what networks are

included in 192.168.32.0 /20� 11000000 10101000 00100000 00000000

� 11000000 10101000 00100000 00000000� 11000000 10101000 00100000 00000000� 11000000 10101000 00100001 00000000� 11000000 10101000 00100010 00000000� …..� …..� 11000000 10101000 00101101 00000000� 11000000 10101000 00101101 00000000� 11000000 10101000 00101110 00000000� 11000000 10101000 00101111 00000000

Answer:29© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

� Answer:

Designing VLSM Addressing 6.4.1

� In this activity, you will use the network address 192 168 1 0/24address 192.168.1.0/24to subnet and provide the IP addressing for a ggiven topology.

30© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 157: Nota CCNA Exp 2 - Routing Protocols and Concepts

Designing VLSM Addressing 6.4.2

� In this activity, you will use the network address 172 16 0 0/16address 172.16.0.0/16to subnet and provide the IP addressing for a ggiven topology.

31© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Designing VLSM Addressing 6.4.2

Th t k h th f ll i dd i i t� The network has the following addressing requirements:� East Network Section

–The N-EAST (Northeast) LAN1 will require 4000 host IP addresses. –The N-EAST (Northeast) LAN2 will require 4000 host IP addresses. –The SE-BR1 (Southeast Branch1) LAN1 will require 1000 host IP addresses. –The SE-BR1 (Southeast Branch1) LAN2 will require 1000 host IP addresses. –The SE-BR2 (Southeast Branch2) LAN1 will require 500 host IP addresses. –The SE-BR2 (Southeast Branch2) LAN2 will require 500 host IP addresses. The SE ST1 (Southeast Satellite1) LAN1 will require 250 host IP addresses–The SE-ST1 (Southeast Satellite1) LAN1 will require 250 host IP addresses.

–The SE-ST1 (Southeast Satellite1) LAN2 will require 250 host IP addresses. –The SE-ST2 (Southeast Satellite2) LAN1 will require 125 host IP addresses. –The SE-ST2 (Southeast Satellite2) LAN2 will require 125 host IP addresses.

� West Network Section� West Network Section–The S-WEST (Southwest) LAN1 will require 4000 host IP addresses. –The S-WEST (Southwest) LAN2 will require 4000 host IP addresses. –The NW-BR1 (Northwest Branch1) LAN1 will require 2000 host IP addresses. –The NW-BR1 (Northwest Branch1) LAN2 will require 2000 host IP addressesThe NW BR1 (Northwest Branch1) LAN2 will require 2000 host IP addresses.–The NW-BR2 (Northwest Branch2) LAN1 will require 1000 host IP addresses. –The NW-BR2 (Northwest Branch2) LAN2 will require 1000 host IP addresses.

� Central Network Section The Central LAN1 will require 8000 host IP addresses

32© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

–The Central LAN1 will require 8000 host IP addresses.–The Central LAN2 will require 4000 host IP addresses.

� The WAN links between each of the routers will require an IP address for each end of the link.

Page 158: Nota CCNA Exp 2 - Routing Protocols and Concepts

Troubleshooting VLSM Addressing 6.4.3

� In this activity, the network address 172.16.128.0/17 was used to provide the IP addressing for a network. VLSM has been used to subnet the address spacepincorrectly.

� You will need to troubleshoot the addressing that wasthe addressing that wasassigned to each subnet to determine where errors are present and determine thepresent and determine thecorrect addressing assignments where needed.

33© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Basic Route Summarization 6.4.4

� In this activity, you are given a network with subnetting and addresssubnetting and addressassignments already completed.

� Your task is to determine summarized routes that can be used to reduce the number of entries in routing tablesentries in routing tables

34© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 159: Nota CCNA Exp 2 - Routing Protocols and Concepts

Challenge Route Summarization 6.4.5

� In this activity, you are given a network with subnetting and addresssubnetting and addressassignments already completed.

� Your task is to determine summarized routes that can be used to reduce the number of entries in routing tablesentries in routing tables

35© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Challenge Route Summarization 6.4.5

Add i T blAddressing Table

� Subnet Network Address � S-WEST LAN1 192.168.7.0/27 � S-WEST LAN2 192.168.7.32/27

Addressing Table � Subnet Network Address � N-EAST LAN1 192.168.5.0/27 � N-EAST LAN2 192 168 5 32/27

� Link from WEST to N-WEST 192.168.7.64/30 � Link from WEST to S-WEST 192.168.7.68/30 � Link from HQ to WEST 192.168.7.72/30 � NW-BR1 LAN1 192.168.7.128/27

N EAST LAN2 192.168.5.32/27� Link from EAST to N-EAST 192.168.5.192/30 � Link from EAST to S-EAST 192.168.5.196/30 � Link from HQ to EAST 192.168.5.200/30 � SE BR1 LAN1 192 168 4 0/26

� NW-BR1 LAN2 192.168.7.160/27 � NW-BR2 LAN1 192.168.7.192/28 � NW-BR2 LAN2 192.168.7.208/28 � Link from N-WEST to NW-BR1 192.168.7.224/30

� SE-BR1 LAN1 192.168.4.0/26� SE-BR1 LAN2 192.168.4.64/26 � SE-BR2 LAN1 192.168.4.128/27 � SE-BR2 LAN2 192.168.4.160/27

Link from N WEST to NW BR1 192.168.7.224/30� Link from N-WEST to NW-BR2 192.168.7.228/30� CENTRAL LAN1 192.168.6.0/25 � CENTRAL LAN2 192.168.6.128/26 � Link from HQ to CENTRAL 192 168 6 192/30

� SE-ST1 LAN1 192.168.4.192/29 � SE-ST1 LAN2 192.168.4.200/29 � SE-ST2 LAN1 192.168.4.208/29 � SE-ST2 LAN2 192.168.4.216/29

� Link from HQ to CENTRAL 192.168.6.192/30� Link from SE-BR2 to SE-ST1 192.168.4.224/30 � Link from SE-BR2 to SE-ST2 192.168.4.228/30 � Link from S-EAST to SE-BR2 192.168.4.232/30 � Link from S-EAST to SE-BR1 192 168 4 236/30

36© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Link from S EAST to SE BR1 192.168.4.236/30

Page 160: Nota CCNA Exp 2 - Routing Protocols and Concepts

Troubleshooting Route Summarization 6.4.6

� In this activity, the LAN IP addressing is already completed for the network. VLSM was used to subnet the address space. The summary routes are yincorrect.

� You will need to troubleshoot the summary routes that

Addressing Table the summary routes thathave been assigned to determine where errors are present and determine the

Router Summary Route Network Address

HQ WEST LANs 172.16.52.0/21

HQ EAST LANs 172.16.56.0/23

WEST HQ LAN 172 16 32 0/19present and determine thecorrect summary routes.

WEST HQ LANs 172.16.32.0/19

WEST EAST LANs 172.16.58.0/23

EAST HQ LANs 172.16.30.0/20

EAST WEST LANs 172 16 48 0/21

37© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

EAST WEST LANs 172.16.48.0/21

ISP HQ, WEST, and EAST LANs 172.16.32.0/18

SSummary� Classful IP addressing

�IPv4 addresses have 2 parts:-Network portion found on left side of an IP addressaddress-Host portion found on right side of an IP addressaddress

�Class A, B, & C addresses were designed to provide IP addresses for different sized organizations�The class of an IP address is determined by the decimal value found in the 1st octet�IP addresses are running out so the use of Classless Inter Domain Routing (CIDR) and Variable Length Subnet Mask (VLSM) are used to try and conserve address space

38© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

(VLSM) are used to try and conserve address space

Page 161: Nota CCNA Exp 2 - Routing Protocols and Concepts

SSummary� Classful Routing Updates

–Subnet masks are not sent in routing updates

� Classless IP addressingClassless IP addressing–Benefit of classless IP addressing

�Can create additional network�Can create additional networkaddresses using a subnet mask that fits your needsy

–Uses Classless Interdomain Routing (CIDR)

39© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Summary

� CIDR� CIDR� Uses IP addresses more efficiently through

use of VLSMuse of VLSM-VLSM is the process of subnetting a subnetsubnetting a subnet

� Allows for route summarizationRoute summarization is-Route summarization isrepresenting multiple contiguous routes with a single routeg

40© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 162: Nota CCNA Exp 2 - Routing Protocols and Concepts

Summary

� Classless Routing UpdatesSubnet masks are included in updatesSubnet masks are included in updates

41© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

RIPv2

Chapter 7: Routing Protocols and ConceptsModified by Hasimi Sallehudin

1© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 163: Nota CCNA Exp 2 - Routing Protocols and Concepts

Objectives

� Encounter and describe the limitations of RIPv1’s cou e a d desc be e a o s o slimitations.

� Apply the basic Routing Information Protocol VersionApply the basic Routing Information Protocol Version 2 (RIPv2) configuration commands and evaluate RIPv2 classless routing updates.

� Analyze router output to see RIPv2 support for VLSM and CIDR

� Identify RIPv2 verification commands and common RIPv2 issues.

� Configure, verify, and troubleshoot RIPv2 in “hands-on” labs

2© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

IntroductionIntroduction� Difference between RIPv1 & RIPv2

�RIPv1�RIPv1•A classful distance vector routing protocol•Does not support discontiguous subnetsDoes not support discontiguous subnets•Does not support VLSM•Does not send subnet mask in routing update•Routing updates are broadcast

�RIPv2•A classless distance vector routing protocol that is an enhancement of RIPv1’s featuresenhancement of RIPv1 s features.•Next hop address is included in updates•Routing updates are multicast (224.0.0.9 vs. 255.255.255.255)

http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/rip.htm

3© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

•The use of authentication is an option

Page 164: Nota CCNA Exp 2 - Routing Protocols and Concepts

Introduction

� Similarities between RIPv1 & RIPv2– Use of timers to prevent routing loopsUse of timers to prevent routing loops– Use of split horizon or split horizon with poison reverse to also help prevent routing loops.– Use of triggered updates when there is a change in the topology for faster convergence.

Maximum hop count of 15 with the hop count of 16 signifying– Maximum hop count of 15, with the hop count of 16 signifying an unreachable network.

4© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

RIP 1 Li it tiRIPv1 Limitations� Lab Topology

3 t t�3 router set up�Topology is discontiguous�There exists a static summary route�Static route information can be injected into routing table updates using redistribution.�Routers 1 & 3 contain VLSMRouters 1 & 3 contain VLSM networks�Remember that both the R1 and R3 routers have subnets that are part of the 172 30 0 0/16 major classfulthe 172.30.0.0/16 major classful network (class B). �Also remember that R1 and R3 are connected to R2 using subnets of the g209.165.200.0/24 major classful network (class C). �This topology is discontiguous and will not converge because

5© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

will not converge because 172.30.0.0/16 is divided by the 209.165.200.0/24.

Page 165: Nota CCNA Exp 2 - Routing Protocols and Concepts

RIP 1 Li it tiRIPv1 Limitations

� The topology shows that R2 has a staticR2 has a static summary route to the 192.168.0.0/16 network. The configuration of this summary route will be

6© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

ydisplayed later in this section.

RIP 1 Li it tiRIPv1 Limitations� Review the VLSM addressing

scheme in the figure As shownscheme in the figure. As shown in the top chart, both R1 and R3 have had the 172.30.0.0/16 network subnetted into /24 subnetssubnets.

–Four of these /24 subnets are assigned: –two to R1 (172.30.1.0/24 and (172.30.2.0/24)–two to R3 (172.30.100.0/24 and 172.30.110.0/24).

I th b tt h t h� In the bottom chart, we have taken the 172.30.200.0/24 subnet and subnetted it again, using the first four bits for gsubnets and the last four bits for hosts. The result is a 255.255.255.240 mask or /28. Subnet 1 and Subnet 2 are

7© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Subnet 1 and Subnet 2 are assigned to R3.

Page 166: Nota CCNA Exp 2 - Routing Protocols and Concepts

RIP 1 LimitationsRIPv1 Limitations� Scenario Continued

S� VLSM-Recall this is sub netting the subnet

� Private IP addresses are on LAN links

� Public IP addresses are used on WAN links (through an ISP, or when inside users

d t t id itneed to access outside sites, a public IP address must be used.)

� Loopback interfaces -These are virtual interfaces that can be pinged and

8© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

that can be pinged and added to routing table

Cisco has set these addresses aside for educational purposes.

RIPv1 Limitations

� Loopback interfaces�Notice that R3 is using loopback interfaces (Lo0, Lo1, and Lo2). �A loopback interface is a software-only interface that is used to emulate a physical interfaceis used to emulate a physical interface.

�Like other interfaces, it can be assigned an IP address. �Loopback interfaces are also used by other routing protocols, such as OSPF, for different purposes. p , , p p

�These uses will be discussed in Chapter 11 OSPF.�In a lab environment, loopback interfaces are useful in creating additional networks without having to add more physical interfaces on the routermore physical interfaces on the router. �A loopback interface can be pinged and the subnet can be advertised in routing updates. �Therefore, loopback interfaces are ideal forTherefore, loopback interfaces are ideal for simulating multiple networks attached to the same router. �In our example, R3 does not need four LAN interfaces to demonstrate multiple subnets and

9© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

interfaces to demonstrate multiple subnets and VLSM. Instead, we use loopback interfaces.

Page 167: Nota CCNA Exp 2 - Routing Protocols and Concepts

RIPv1 LimitationsRIPv1 Limitations� Route redistribution

Redistribution involves taking the routes from one routing– Redistribution involves taking the routes from one routing source and sending those routes to another routing source.

• In our example topology, we want the RIP process on R2 to redistribute our static route (192.168.0.0/16) by importing the route into RIP and then sending it to R1 and R3 using the RIP process.

R2( fi t )# di t ib t t ti-R2(config-router)#redistribute static

10© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

RIPv1 LimitationsRIPv1 Limitations� R2(config)#ip route 192.168.0.0 255.255.0.0 Null0

The address space represented by the static summary route–The address space represented by the static summary route 192.168.0.0/16 does not actually exist. –In order to simulate this static route, we use a null interface as the exit interface.– You do not need to enter any commands to create or configure the null interfaceconfigure the null interface. –It is always up but does not forward or receive traffic. Traffic sent to the null interface is discarded.

11© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 168: Nota CCNA Exp 2 - Routing Protocols and Concepts

Static routes and null interfaces

� Static routes and null interfacesStat c outes a d u te acesR2(config)#ip route 192.168.0.0 255.255.0.0 Null0

�a static route must have an active exit interfacea static route must have an active exit interface before it will be installed in the routing table. �Using the null interface will allow R2 to advertise the gstatic route in RIP even though networks belonging to the summary 192.168.0.0/16 do not actually exist.

12© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

V if i d T ti C ti itVerifying and Testing Connectivity� show ip interfaces brief

T t t h th t th t l h f ll–To test whether or not the topology has full connectivity, we first verify that both serial links on R2 are up using the show ip interface brief

� Ping�Whenever R2 pings any of the 172.30.0.0 subnets on R1 or R3, only about 50% of the ICMP are successful.�R1 is able to ping 10.1.0.1 but is unsuccessful when attempting to ping the 172.30.100.1 on R3�R3 is able to ping 10 1 0 1 but is unsuccessful�R3 is able to ping 10.1.0.1 but is unsuccessful when attempting to ping the 172.30.1.1 on R1.

13© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 169: Nota CCNA Exp 2 - Routing Protocols and Concepts

RIP 1 Li it tiRIPv1 Limitations� RIPv1 – a classful routing protocol

–Subnet mask are not sent in updatesSubnet mask are not sent in updates–Summarizes networks at major network boundaries–RIPv1 cannot support discontiguous networks, VLSM, or CIDR.

if t k i di ti d RIP 1 fi d ill t b–if network is discontiguous and RIPv1 configured convergence will not be reached–RIPv1 on both the R1 and R3 routers will summarize their 172.30.0.0 subnets to the classful major network address of 172 30 0 0 when sendingsubnets to the classful major network address of 172.30.0.0 when sending routing updates to R2. –From the perspective of R2, both updates have an equal cost of 1 hop to reach network 172 30 0 0/16 As you will see R2 installs both paths in thereach network 172.30.0.0/16. As you will see, R2 installs both paths in the routing table.

14© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

RIP 1 Li it tiRIPv1 Limitations�Examining the routing tables

-To examine the contents of routing updates use the debug ip rip command

R2 i i i t 172 30 0 0 l tR2 is receiving two 172.30.0.0 equal cost routes with a metric of 1 hop. R2 is receiving one route on Serial 0/0/0 from R1 and the other route on Serial 0/0/1 from R3.

R2 has two equal cost routes to the 172.30.0.0/16 network.

15© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 170: Nota CCNA Exp 2 - Routing Protocols and Concepts

RIP 1 Li it tiRIPv1 Limitations

•R1 has its own 172 30 0 0 routes:•R1 has its own 172.30.0.0 routes: 172.30.2.0/24 and 172.30.1.0/24. •But R1 does not send R2 those subnets. •R3 has a similar routing table. B th R1 d R3 b d t d•Both R1 and R3 are boundary routers and

are only sending the summarized 172.30.0.0 network to R2 in their RIPv1 routing updates. A lt R2 l k b t th

•R2 that it is not including the 172.30.0.0 network in its updates to either R1 or R3. •Because the split horizon rule is in effect. •R2 learned about 172 30 0 0/16 on both the•As a result, R2 only knows about the

172.30.0.0/16 classful network and is unaware of any 172.30.0.0 subnets.

•R2 learned about 172.30.0.0/16 on both the Serial 0/0/0 and Serial 0/0/1 interfaces, it does not include that network in updates it sends out these same interfaces.

16© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

RIPv1 LimitationsRIPv1 Limitations� Because RIPv1 does not send the

subnet mask in routing updates, it R4 is added tog pcannot support VLSM.

� R3 router is configured with VLSM subnets all of which are members

R4 is added to the topology connected to R3

subnets, all of which are members of the class B network 172.30.0.0/16:

–172.30.100.0/24 (FastEthernet 0/0)172.30.100.0/24 (FastEthernet 0/0)–172.30.110.0/24 (Loopback 0)–172.30.200.16/28 (Loopback 1)

172 30 200 32/28 (L b k 2)–172.30.200.32/28 (Loopback 2)

� As we saw with the 172.30.0.0/16 updates to R2 by R3, p y

–RIPv1 either summarizes the subnets to the classful boundary –or uses the subnet mask of the

17© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

o uses t e sub et as o t eoutgoing interface to determine which subnets to advertise.

Page 171: Nota CCNA Exp 2 - Routing Protocols and Concepts

RIPv1 LimitationsRIPv1 Limitations� Why is RIPv1 on R3 not including

the other subnets, 172 30 200 16/28 and R4 is added to172.30.200.16/28 and 172.30.200.32/28, in updates to R4?

– Those subnets do not have the

R4 is added to the topology connected to R3

Those subnets do not have the same subnet mask as FastEthernet 0/0.

– R3 will only include those 172 30 0 0 routes in its routing172.30.0.0 routes in its routing table with the same mask as the exit interface.

– Since the interface is 172.30.100.1 ith /24 k it ill l i l dwith a /24 mask, it will only include

172.30.0.0 subnets with a /24 mask. The only one that meets this condition is 172.30.110.0.

– The other 172.30.0.0 subnets, 172.30.200.16/28 and 172.30.200.32/28, are not included because the /28 masks

18© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

do not match the /24 mask of the outgoing interface.

RIP 1 Li it tiRIPv1 Limitations� No CIDR Support

R2(config)#ip route 192 168 0 0R2(config)#ip route 192.168.0.0 255.255.0.0 Null0–the static route is included in R2's routing table, but R2 will not include the static route in itsnot include the static route in its update –R1 is not receiving this 192.168.0.0/16 route in its RIP updates from R2,

� Reason: Classful routing protocols do not support p ppCIDR routes that are summarized with a smaller mask than the classful

b t ksubnet mask–If the 192.168.0.0 static route were configured with a /24 mask or greater, this route would be

19© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

g ,included in the RIP updates.

Page 172: Nota CCNA Exp 2 - Routing Protocols and Concepts

Config ring RIP 2Configuring RIPv2� Comparing RIPv1 & RIPv2 Message Formats

–RIPv2 Message format is similar to RIPv1 but has 2 extensionsg1st extension is the subnet mask field

�allows a 32 bit mask to be included in the RIP route entry.�the receiving router no longer depends upon the subnet mask of thethe receiving router no longer depends upon the subnet mask of the inbound interface or the classful mask when determining the subnet mask for a route

2nd extension is the addition of next hop address�The Next Hop address is used to identify a better next-hop address - if one exists - than the address of the sending router. �If the field is set to all zeros (0.0.0.0), the address of the sending router is the best next-hop addressis the best next-hop address.

20© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Configuring RIPv2

� Enabling and Verifying RIPv2� Enabling and Verifying RIPv2

� Configuring RIP on a Cisco router–By default it is running RIPv1–Even though the router only sends RIPv1 messages, it can interpret both RIPv1 and RIPv2 messagesinterpret both RIPv1 and RIPv2 messages. –A RIPv1 router will just ignore the RIPv2 fields in the route entry. RIPv1 RIPv2RIPv1 RIPv2

21© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 173: Nota CCNA Exp 2 - Routing Protocols and Concepts

Configuring RIPv2Configuring RIPv2

� Configuring RIPv2 on aConfiguring RIPv2 on a Cisco router

-Requires using the-Requires using the version 2 command

RIPv2 ignores RIPv1-RIPv2 ignores RIPv1 updates

� To verify RIPv2 is� To verify RIPv2 is configured use the

show ip protocolsshow ip protocolscommand

22© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Comparing RIP v1 and v2Comparing RIP v1 and v2� RIP v2 �� send and receive v2

� RIP v1 � send v1 but can receive both v1 and v2RIP v1 � send v1 but can receive both v1 and v2

No I can notI l dRIP network is broken

Version 1 Version 2

No. I can not take version 1

I can only send version 1

Version 1 Version 2

Yes. I can take version 1 or 2 I can only send

version 2

23© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 174: Nota CCNA Exp 2 - Routing Protocols and Concepts

POP QuizPOP Quiz� How do you make the RIPv2 back to the default “send 1” and

receive 1 or 2”?- Hint: Gad(config-router)#version 1 is not the answer.

Version 1 Version 2Version 1 Version 2

24© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

C fi i RIP 2Configuring RIPv2� Auto-Summary & RIPv2Auto Summary & RIPv2

� RIPv2 will automatically summarize routes at majorsummarize routes at major network boundaries andcan also summarize routes with a subnet mask that is smaller than the classful subnet masksubnet mask

25© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 175: Nota CCNA Exp 2 - Routing Protocols and Concepts

Configuring RIPv2Configuring RIPv2

� Disabling Auto-Summary in RIPv2

� To disable automatic summarization issue th tthe no auto-summarycommand

26© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Configuring RIPv2

� Verifying RIPv2 Updates

� When using RIPv2 with automatic summarization turned off

Each subnet and mask has its own specific entry, along with the exit interface and next-hop address to reach that subnet.

� To verify information being sent by RIPv2 use they g y

debug ip rip command

27© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 176: Nota CCNA Exp 2 - Routing Protocols and Concepts

VLSM & CIDRVLSM & CIDR

� RIPv2 and VLSM

� Networks using a VLSM IPNetworks using a VLSM IP addressing scheme

Use classlessUse classless routing protocols (i.e. RIPv2) to disseminate network addresses and their subnetand their subnet masks

28© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

VLSM & CIDR

� CIDR uses Supernetting

S tti i b h f ti l f lSupernetting is a bunch of contiguous classful networks that is addressed as a single network.network.

29© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 177: Nota CCNA Exp 2 - Routing Protocols and Concepts

VLSM & CIDR

� To verify that supernets are being sent andbeing sent and received use the following commands

-Show ip route

Debug ip rip-Debug ip rip

30© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Verifying & Troubleshooting RIPv2Verifying & Troubleshooting RIPv2� Basic Troubleshooting steps

-Check the status of all links

-Check cablingCheck cabling

-Check IP address & subnet mask configuration

-Remove any unneeded configuration commands

� Commands used to verify proper operation of RIPv2–Show ip interfaces brief–Show ip protocolsp p–Debug ip rip–Show ip route

31© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

–Show ip route

Page 178: Nota CCNA Exp 2 - Routing Protocols and Concepts

Verifying & Troubleshooting RIPv2

C RIP 2 I� Common RIPv2 Issues

� When trouble shooting RIPv2 examine the following issues:�Version

Check to make sure you are using version 2�Network statements

Network statements may be incorrectly typed y y ypor missing

�Automatic summarization

If summarized routes are not needed then disable automatic summarization

32© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

V if i & T bl h ti RIP 2Verifying & Troubleshooting RIPv2� Reasons why it’s good to authenticate routing information y g g

-Prevent the possibility of accepting invalid routing updates

-Contents of routing updates are encryptedg p yp

� Types of routing protocols that can use authentication

-RIPv2RIPv2

-EIGRP

-OSPFOSPF

-IS-IS

-BGP-BGP

33© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 179: Nota CCNA Exp 2 - Routing Protocols and Concepts

Summary

RoutingProtocol

DistanceVector

ClasslessRoutingProtocol

UsesHold-Down

Use ofSplit

Horizon

MaxHop

count

AutoSummary

SupportCIDR

SupportsVLSM

Uses Authen-tication

Timers orSplit

Horizon w/

Poison

= 15

Poison Reverse

RIPv1 Yes No Yes Yes Yes Yes No No No

RIPv2 Yes Yes Yes Yes Yes Yes Yes Yes Yes

34© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

The Routing Table: A Closer Look

Chapter 8: Routing Protocols and Concepts

Modified by Hasimi Sallehudin

1© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 180: Nota CCNA Exp 2 - Routing Protocols and Concepts

Objectives

� Describe the various route types found in the routingesc be e a ous ou e ypes ou d e ou gtable structure

� Describe the routing table lookup process.Describe the routing table lookup process.

� Describe routing behavior in routed networks.

2© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Introduction

� Chapter Focus– Structure of the routing tableStructure of the routing table

•Will examine the format of the routing table and learn about level 1 and level 2 routes.

– Lookup process of the routing table– Classless and classful routing behaviors

Cisco IP Routing by Alex Zinin (ISBN 0-201-60473-6)Cisco IP Routing, by Alex Zinin (ISBN 0 201 60473 6).

3© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 181: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table StructureRouting Table Structure� Lab Topology

� 3 router setup-R1 and R2 share a common 172.16.0.0/16 network with 172 16 2 0/24 subnets172.16.2.0/24 subnets.-R2 and R3 are connected by the 192.168.1.0/24 network.-R3 also has a 172 16 4 0/24 subnet which is disconnected orR3 also has a 172.16.4.0/24 subnet, which is disconnected, ordiscontiguous, from the 172.16.0.0 network that R1 and R2 share.

4© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

In a later section, we will configure the interfaces for R2

Routing Table Structure

� The figure shows routing table entries come from the� The figure shows routing table entries come from thefollowing sources

-Directly connected networks-Directly connected networks-Static routesDynamic routing protocols-Dynamic routing protocols

5© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 182: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table StructureRouting Table Structure� The figure shows what happens as the Serial 0/0/1 interface for R2 is

configured with the 192.168.1.1/24 address. – R1 and R3 already have their interfaces configured with the appropriate IP addresses and subnet masks.–We will now configure the interfaces for R2 and use debug ip routing to view the routing table process that is used to add these entries.

� As soon as the “no shutdown” command is issued the route is added to routing table g

debug ip routingdebug ip routing

6© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing Table Structure

Ci IP ti t bl� Cisco IP routing tableis a hierarchical structurestructure

–The reason for this is to speed up lookupto speed up lookupprocess

The hierarchy–The hierarchyincludes several levels.

•level 1 •level 2

7© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

level 2

Page 183: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table StructureRouting Table Structure� Level 1 Routes

–Have a subnet mask equal to or less than the classful qmask of the network address.–192.168.1.0/24 is a level 1 network route, because the subnet mask is equal to the network's classful mask. /24 f l C t k h th 192 168 1 0 t kfor class C networks, such as the 192.168.1.0 network.

� Level 1 route can function as–Default route

•A default route is a static route with the address 0.0.0.0/0.

–Supernet routeS p•A supernet route is a network address with a mask less than the classful mask.

–Network routeNetwork route•A network route is a route that has a subnet mask equal to that of the classful mask.

� The source of the level 1 route can be a directly

8© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

� The source of the level 1 route can be a directlyconnected network, static route, or a dynamic routing protocol.

Routing Table StructureRouting Table Structure� The level 1 route 192.168.1.0/24 can be further defined as an

ultimate route.ultimate route.�ultimate route includes either:

-A next-hop ip address (another path)OROR

-An exit interface� The directly connected network 192.168.1.0/24

It i l l 1 t k t b it h b t k th t i th–It is a level 1 network route because it has a subnet mask that is the same as its classful mask.–This same route is also an ultimate route because it contains the exit interface Serial 0/0/1Serial 0/0/1.

9© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 184: Nota CCNA Exp 2 - Routing Protocols and Concepts

Parent and Child Routes� A parent route is a level 1 route

Parent and Child Routes

–A parent route does not containany next-hop IP address or exitinterface information

� When the 172.16.3.0 subnet was added to the routing table, another route, 172.16.0.0, was also added. , ,

–The first entry, 172.16.0.0/24, does not contain any next-hop IP address or exit interface information.or exit interface information.–This route is known as a level 1 parent route.

A t t i t ll h di–A parent route is actually a headingthat indicates the presence of level 2 routes, also known as child routes.

10© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing Table StructureRouting Table Structure� A level 1 parent route is automatically

created any time a subnet is added tocreated any time a subnet is added tothe routing table.

–In other words, a parent route is created whenever a route with a maskcreated whenever a route with a maskgreater than the classful mask is entered into the routing table.

172 16 0 0/24 i b tt d 1 b t–172.16.0.0/24 is subnetted, 1 subnets

� A level 2 route is a route that is a subnet of a classful network address.

– Child routes are level 2 routes– Child routes are a subnet of a l f l t k ddclassful network address

–C 172.16.3.0 is directly connected, FastEthernet0/0

11© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 185: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table StructureRouting Table Structure� The parent route contains the 172.16.0.0 - The classful network

address for our subnet.

� Level 2 child routes contain 172.16.3.0, route source & the network address of the route

–Notice that the subnet mask is not included with the subnet the level–Notice that the subnet mask is not included with the subnet, the level2 child route. The subnet mask for this child route (subnet) is the /24 mask included in its parent route, 172.16.0.0

� Level 2 child routes are also considered ultimate routes� Level 2 child routes are also considered ultimate routes–Reason: they contain the next hop address &/or exit interface

12© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing Table StructureRouting Table Structure� The figure shows the

configuration of the Serialconfiguration of the Serial0/0/0 interface on R2.

–The routing table showsThe routing table showstwo child routes for the same 172.16.0.0/24 parent routeroute.

•Both 172.16.2.0 and 172.16.3.0 are members of the same parent route, •because they are both

b f thmembers of the172.16.0.0/16 classful network

13© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 186: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table Structure

� Both child routes have the same subnet mask

-This means the parent route maintains the /24 mask

Note: If there is only a single level 2 child route and that route isand that route isremoved, the level 1 parent route will be automatically deleted. A level 1 parent route exists only when there is at least one level 2 child route

14© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

child route.

The role of the parent route will be examined when we discuss the route lookup process.

Routing Table Structure� In classless networks, child routes do not have to share

the same subnet mask–Whenever there are two or more child routes with different subnet masks belonging to the same classful network thesubnet masks belonging to the same classful network, therouting table presents a slightly different view, which states that this parent network is variably subnetted.

15© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 187: Nota CCNA Exp 2 - Routing Protocols and Concepts

R ti T bl St tRouting Table Structure

� Parent & Child Routes: Classless Networks� Parent & Child Routes: Classless Networks

16© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing Table Structure

� Parent & Child Routes: classful and classless NetworksParent & Child Routes: classful and classless Networks

NetworkType

Parentroute’s

Term variably

Includesthe # of

Subnetmask

classful

Classfulmask is

Displayed

subnetted is seen in

parentroute in routing

differentmasks of

childroutes

includedwith each

child route entry

routingtable

Class-ful

No No No No classless

Class-l

Yes Yes Yes Yesless

17© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 188: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table Lookup ProcessRouting Table Lookup Process� The Route Lookup Process

1. Examine level 1 routes• If best match a level 1 ultimate route

and is not a parent route this route is used to forward packet

• If the best match is a level 1 parent• If the best match is a level 1 parentroute, proceed to Step 2

2. Router examines level 2 (child) routes• If there is a match with level 2 child

route then that subnet is used to forward packet

• If no match then proceed to Step 33 R t d t i l f l3. Router determines classful or

classless routing behavior• If classful then packet is dropped• If classless then router searches level• If classless then router searches level

one supernet and default routes4. If there exists a level 1 supernet or

default route match then Packet is f d d

18© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

forwarded5. If not packet is dropped

R ti T bl L k PRouting Table Lookup Process� Longest Match: Level 1 Network Routes

Best match is also known as the longest match–Best match is also known as the longest match–The best match is the one that has the most number of left most bits matching between the destination IP address and the route in the routing table.

� For example, in the figure we have a packet destined for 172 16 0 10 Many possible routes could match this packet Three172.16.0.10. Many possible routes could match this packet. Threepossible routes are shown that do match this packet: 172.16.0.0/12, 172.16.0.0/18, and 172.16.0.0/26. Of the three routes, 172 16 0 0/26 has the longest match172.16.0.0/26 has the longest match.

19© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 189: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table Lookup ProcessRouting Table Lookup Process� Finding the subnet mask

used to determine theused to determine thelongest match

Scenario:Scenario:–PC1 pings 192.168.1.2–Router examines level 1

t f b t t hroute for best match–There exist a match between192.168.1.2 & 192.168.1.0 / 24–Router forwards packets out s0/0/0

20© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing Table Lookup ProcessRouting Table Lookup Process� The process of matching

–1st there must be a match made between the parent route & destination IP

•If a match is made then an attempt at finding a match•If a match is made then an attempt at finding a matchbetween the destination IP and the child route is made.•Do at least 16 of the left-most bits of the parent route match the pfirst 16 bits of the packet's destination IP address of 192.168.1.2?

–The answer, no,

21© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 190: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table Lookup Process

Fi di t h b t k t’ d ti ti IP dd� Finding a match between packet’s destination IP addressand the next route in the routing table

The figure shows a match between the destination IP of 192 168 1 0–The figure shows a match between the destination IP of 192.168.1.0and the level one IP of 192.168.1.0 / 24 then packet forwarded out s0/0/0–Not only does the minimum of 24 bits match, but a total of 30 bits match, as shown in the figure.

22© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing Table Lookup Process� In the example in the figure, PC1 sends a ping to PC2 p g , p g

at 172.16.3.10. What happens when there is a match with a level 1 parent route?B f l l 2 hild t i d� Before level 2 child routes are examined

-There must be a match between classful level one parent route and destination IP addressparent route and destination IP address.

23© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 191: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table Lookup ProcessRouting Table Lookup Process� After the match with parent route has been made Level 2 child

routes will be examined for a matchroutes will be examined for a match

-Route lookup process searches for child routes with a match with destination IP

24© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing Table Lookup ProcessRouting Table Lookup Process� How a router finds a match with one of the level 2

child routeschild routes–First router examines parent routes for a match–If a match exists then:

Child routes are examined•Child routes are examined•Child route chosen is the one with the longest match

� First, the router examines the parent route for a match.

� The router checks the last child route forThe router checks the last child route for172.16.3.0/24 and finds a match. The first 24 bits do match. The routing table process will use this route, 172.16.3.0/24, to forward the packet with the destination IP address of 172.16.3.10 out the exit interface of Serial 0/0/0.

� R 172.16.3.0 [120/1] via 172.16.2.2, 00:00:25,

25© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

R 172.16.3.0 [120/1] via 172.16.2.2, 00:00:25,Serial0/0/0

Page 192: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Table Lookup ProcessRouting Table Lookup Process

� Example: Route Lookup� Example: Route LookupProcess with VLSM

The use of VLSM does not-The use of VLSM does notchange the lookup process

-If there is a match betweenIf there is a match betweendestination IP address and the level 1 parent route then

-Level 2 child routes will be searched

26© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing BehaviorRouting Behavior� Classful & classless routing protocols

Influence how routing table is populated� Classful & classless routing behaviors

Determines how routing table is searched after it is filled

27© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 193: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing BehaviorRouting Behavior� Classful Routing

Behavior: no ipBehavior: no ipclassless

� What happens if there isppnot a match with any level 2 child routes of the parent?parent?-Router must determine if the routing behavior is gclassless or classful

-If router is utilizing classfulrouting behavior thenrouting behavior then

-Lookup process is terminated and ip classless and no ip classless

28© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

terminated andpacket is dropped

ip classless and no ip classless

Using the ip classless command (cont.)g ( )

What is IP Classless?� The "ip classless" command prevents the existence of a single "subnet" route from blocking access via the

http://www.networkking.net/out/IPClassless.htmp p g g

default route to other subnets of the same old-style network. Default only works with single-homed ISPs.� RFC 1879

� IP classless command is not easy to understand, we know that. But I bet, after you read the following lines, you will understand what it is all about.

� First, you must understand a very simple logic. Here is the logic: Me and you are on a journey. If you break my leg, then you must carry me all the way! If you understand this logic, you will understand "IP classless".

� RIP is telling you: I am classful, if you break my class, then you have to show me every route there is, or I will drop your packet. I will drop it even though there is a default route (0.0.0.0).

� What is classful? Classful means that a class A subnet should be shown as x 0 0 0 such as 10 0 0 0 255 0 0 0� What is classful? Classful means that a class A subnet should be shown as x.0.0.0 such as 10.0.0.0 255.0.0.0� If you show it as 10.44.0.0 255.255.0.0, you are breaking its class.� Or, a class B subnet should be shown as x.x.0.0 255.255.0.0 such as 172.29.0.0 255.255.0.0� If you show it as 172.29.26.0 255.255.255.0, you are breaking its class.� Let’s assume RIP knows about 10.0.0.0� If you break 10.0.0.0 into three, for example to 10.1.0.0 and 10.2.0.0 and 10.3.0.0, and then give RIP a packet with a

destination of 10.4.0.1, RIP will drop it. Why? Why doesn’t RIP send the packet to the default route? � Because RIP told you, if you break my class, then you have to show me every damn route, otherwise I will drop it.

Here you broke RIP's class so you must show him the way to 10 4 0 1 and every other 10 x x x route in the universeHere, you broke RIP s class so you must show him the way to 10.4.0.1 and every other 10.x.x.x route in the universe.Otherwise RIP will drop the packet, even if there is a default route. RIP will not care about your default route or last resort gateway; it will drop your packet.

� How do you ask RIP not to drop your packet and send the unknown destinations to the default route, although you have been so mean to him and have broken its class? You tell him: please, please, ip classless!If i l l d th k t

29© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

� If no ip classless, drop the packet

If ip classless, send the packet to the default.

Page 194: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing BehaviorRouting Behavior� ip Classless

� Beginning with IOS 11.3, “ip classless”was configured by default

–The command “no ip classless” means that the route lookup process uses classful routing tablelookups by defaultlookups by default.

� Classless routing behavior works for Di ti t k-Discontiguous networks

AndCIDR t-CIDR supernets

30© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing Behavior “no ip classless”Routing Behavior� Classful Routing Behavior – Search Process

–when classful routing behavior is in effect (no ip

no ip classless

g ( pclassless) the process will not continue searching level 1 routes in the routing table. If a packet doesn't match a child route for the parent network route, then the router drops the packetthe router drops the packet.

� R2 receives a packet destined for PC3 at 172.16.4.10.

–Even with the default route configured. –The destination’s subnet mask is a /24 and none of the child routes left most bits match the first 24 bits.Thi k t i d dThis means packet is dropped

31© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 195: Nota CCNA Exp 2 - Routing Protocols and Concepts

R ti B h iRouting Behavior� Classful Routing Behavior – Search

P

“no ip classless”

Process� The reason why the router will not search

beyond the child routesy�At the beginning of the Internet's growth, networks were all classful�This meant an organization could�This meant an organization couldsubnet a major network address and “enlighten” all the organization’s routers about the subnettingrouters about the subnetting�Therefore, if the subnet was not in the routing table, the subnet did not exist and packet was droppedand packet was dropped

� The routing table process will not use the default route, 0.0.0.0/0, or any other route

32© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

route.

R ti B h iRouting Behavior� The routing table process will not

“no ip classless”g p

use the default route, 0.0.0.0/0, or any other route.

�A common error is to assume that a default route will always be used if the router does not have a better route. �In our example, R2's default route is not examined nor used, although it is a matchmatch.� This is often a very surprising result when a network administrator does not

d t d th diff b tunderstand the difference betweenclassful and classless routing behavior.

33© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 196: Nota CCNA Exp 2 - Routing Protocols and Concepts

Ro ting Beha iorRouting Behavior� Classless Routing Behavior-

“ip classless”g

ip lassless� Step 3: If classless routing behavior inStep 3: If classless routing behavior in

effect then, continue searching level 1 supernet routes in the routing table for a match including the default route if there ismatch, including the default route, if there isone.

� Step 4: Match with supernet or default�Supernet routes Checked first–If a match exists then forward packet

�Default routes Checked second

� Step 5: If there is no match or no default t th th Packet is dropped

34© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

route then the Packet is dropped

R ti B h iRouting Behavior� Classless Routing Behavior – Search Process

“ip classless”g

� Router begins search process by finding a match between destination IP and parent route

After finding the above mentioned match, then there is a search of the child route

� There is no match with the level 2 child routes� There is no match with the level 2 child routes.

35© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 197: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing BehaviorRouting Behavior� If no match is found in child routes of

previous slide then

“ip classless”

previous slide then–Router continues to search the routing table for a match that may h f th 16 bit i th t hhave fewer than 16 bits in the match

� The 192.168.1.0/24 route does not have 24 left-most bits that match thehave 24 left-most bits that match thedestination IP address.

C 192.168.1.0/24 is directly connected, Serial0/0/1

36© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Routing BehaviorRouting BehaviorS* 0.0.0.0/0 is directly connected, Serial0/0/1

“ip classless”

� The mask is /0, which means that zero or no bits need to match.

� A default route will be the lowest-bit match. In classless routing behavior, if no other route matches the default routeroute matches, the default routewill match.

–In this case the router will use theIn this case the router will use thedefault route, because it is the best match. The packet will be forwarded out the Serial 0/0/1 interface.

37© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

out the Serial 0/0/1 interface.

Page 198: Nota CCNA Exp 2 - Routing Protocols and Concepts

Routing Behavior

� What does R3 do with return traffic back to PC2 at 172 16 2 10?172.16.2.10?

� In this case, R3 uses the 172.16.0.0/16 child route and f d th t ffi t S i lforwards the traffic out Serial0/0/1 back to R2.

38© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

R ti B h iRouting Behavior� Classful vs. Classless Routing Behavior

-It is recommended to use classless routing behavior

�Reason: so supernet and default routes can be used whenever needed

39© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 199: Nota CCNA Exp 2 - Routing Protocols and Concepts

O QLongest Match http://www.cisco.com/warp/public/105/21.html

POP QUIZp p p

� Let's look at the three routes we just installed in the routing table, and see how they look on the router.

� router# show ip route....D 192.168.32.0/26 [90/25789217] via 10.1.1.1 ----� (192.168.32.0 to 192.168.32.63)[ ] ( )R 192.168.32.0/24 [120/4] via 10.1.1.2 ----� (192.168.32.0 to 192.168.32.255)O 192.168.32.0/19 [110/229840] via 10.1.1.3 ----� (192.168.32.0 to 192.168.63.255)....

� If a packet arrives on a router interface destined for 192.168.32.1, which route would the router choose?

� If a packet arrives on a router interface destined for 192.168.32.100,which route would the router choose?

40© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Answers are on the next page

Longest MatchLongest Matchhttp://www.cisco.com/warp/public/105/21.html

� Let's look at the three routes we just installed in the routing table, and see how j g ,they look on the router.

� router# show ip route....D 192.168.32.0/26 [90/25789217] via 10.1.1.1 ----� (192.168.32.0 to 192.168.32.63)R 192.168.32.0/24 [120/4] via 10.1.1.2 ----� (192.168.32.0 to 192.168.32.255)O 192.168.32.0/19 [110/229840] via 10.1.1.3 ----� (192.168.32.0 to 192.168.63.255)....

� If a packet destined to 192.168.32.1 is directed toward 10.1.1.1, because 192.168.32.1 falls within the 192.168.32.0/26 network (192.168.32.0 to 192 168 32 63) It also falls within the other two routes available but the192.168.32.63). It also falls within the other two routes available, but the192.168.32.0/26 has the longest prefix within the routing table (26 bits verses 24 or 19 bits).

� if a packet destined for 192.168.32.100 arrives on one of the router's interfaces, f fp

it's forwarded to 10.1.1.2, because 192.168.32.100 doesn't fall within 192.168.32.0/26 (192.168.32.0 through 192.168.32.63), but it does fall within the 192.168.32.0/24 destination (192.168.32.0 through 192.168.32.255). Again, it also falls into the range covered by 192.168.32.0/19, but 192.168.32.0/24 has a longer

fi l th

41© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

prefix length

Page 200: Nota CCNA Exp 2 - Routing Protocols and Concepts

Summary

Content/str ct re of a ro ting tableContent/structure of a routing table� Routing table entries

Directly connected networks-Directly connected networks-Static route-Dynamic routing protocolsDynamic routing protocols

� Routing tables are hierarchical-Level 1 route

Have a subnet mask that is less than or equal to classful subnet mask for the network address

L l 2 t-Level 2 routeThese are subnets of a network address

42© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

SummarySummaryRouting table lookup process� Begins with examining level 1 routes for best match with packet’s destination IPBegins with examining level 1 routes for best match with packet s destination IP

� If the best match = an ultimate route then-Packet is forwarded -Else--Parent route is examined-Parent route is examined

If parent route & destination IP match then Level 2 (child) routes are examined

Level 2 route examinationLevel 2 route examination� If a match between destination IP and child route found then

Packet forwarded -Else � If Router is using classful routing behavior then g g

Packet is dropped -Else

� If router is using classless routing behavior thenRouter searches Level 1 supernet & default routes for a match

� If a match is found then Packet if forwarded -Else� Packet is dropped

43© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Packet is dropped

Page 201: Nota CCNA Exp 2 - Routing Protocols and Concepts

Summary

� Routing behaviors

-This refers to how a routing table is searched

� Classful routing behavior

-Indicated by the use of the no ip classless commandy p

-Router will not look beyond child routes for a lesser match

� Classless routing behavior

-Indicated by the use of the ip classless commandIndicated by the use of the ip classless command

-Router will look beyond child routes for a lesser match

44© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

EIGRP

Chapter 9: Routing Protocols and Concepts

Modified by Hasimi Sallehudin

1© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 202: Nota CCNA Exp 2 - Routing Protocols and Concepts

IntroductionIntroduction

2© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

EIGRP

� Roots of EIGRP: IGRP-Developed in 1985 to overcome RIPv1’s limited hop count-Distance vector routing protocolM t i d b IGRP-Metrics used by IGRP

�bandwidth (used by default)�Delay (used by default)�Delay (used by default)�Reliability (not used by default)�Load (not used by default)Load (not used by default)

-Discontinued support starting with IOS 12.2(13)T & 12.2(R1s4)S

3© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 203: Nota CCNA Exp 2 - Routing Protocols and Concepts

EIGRP

� EIGRP is a distance vector, classless routing protocol that was released in 1992 with IOS 9 21released in 1992 with IOS 9.21.

� As its name suggests, EIGRP is an enhancement of Cisco IGRP (Interior Gateway Routing Protocol).

� Both are Cisco proprietary protocols and only operate on CiscoBoth are Cisco proprietary protocols and only operate on Ciscorouters.

� The main purpose in Cisco's development of EIGRP was to create a classless version of IGRP. EIGRP includes several features that are not commonly found in other distance vectorfeatures that are not commonly found in other distance vectorrouting protocols like RIP (RIPv1 and RIPv2) and IGRP. These features include:

–Reliable Transport Protocol (RTP)–Bounded Updatesp–Diffusing Update Algorithm (DUAL)–Establishing Adjacencies–Neighbor and Topology Tables

Alth h EIGRP t lik li k t t ti t l it i� Although EIGRP may act like a link-state routing protocol, it isstill a distance vector routing protocol.

–Note: The term hybrid routing protocol is sometimes used to define EIGRP. However, this term is misleading because EIGRP is not a hybrid between distance vector and link-state routing protocols - it is

4© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

hybrid between distance vector and link state routing protocols it issolely a distance vector routing protocol. Therefore, Cisco is no longer using this term to refer to EIGRP.

EIGRP

� The Algorithm� The Algorithm–EIGRP uses the Diffusing Update Algorithm (DUAL).–EIGRP does not send periodic updates and route entries do not age outout.–Only changes in the routing information, such as a new link or a li k b i il bllink becoming unavailable cause a routing update to occur. –EIGRP routing updates are still g pvectors of distances transmitted to directly connected neighbors.

5© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 204: Nota CCNA Exp 2 - Routing Protocols and Concepts

EIGRP� Path Determination

G–EIGRP's DUAL maintains a topologytable separate from the routing table, which includes both the best path to a destination network and any backupdestination network and any backuppaths that DUAL has determined to be loop-free.

If a route becomes unavailable DUAL–If a route becomes unavailable, DUALwill search its topology table for a valid backup path.

If i t th t t i•If one exists, that route isimmediately entered into the routing table.If d t i t DUAL f•If one does not exist, DUAL performs

a network discovery process to see if there happens to be a backup path that did not meet the requirement of

6© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

that did not meet the requirement ofthe feasibility condition.

EIGRP� Convergence

–EIGRP does not use holddown timers.

Instead loop free paths are–Instead, loop-free paths areachieved through a system of route calculations (diffusing computations) that are performed in a coordinatedthat are performed in a coordinatedfashion among the routers. –The detail of how this is done is beyond the scope of this course, but the result is faster convergence than traditional distance vector routing protocols.

7© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 205: Nota CCNA Exp 2 - Routing Protocols and Concepts

EIGRPEIGRPEIGRP Message Format� EIGRP HeaderEIGRP Header

�Data link frame header - contains source and destination MAC address�IP packet header - contains source & destination IP address�EIGRP packet header - contains AS numberAS number�Type/Length/Field - data portion of EIGRP message�In the IP packet header,p ,

�the protocol field is set to 88 to indicate EIGRP�the destination address is set to th lti t 224 0 0 10the multicast 224.0.0.10.

�If the EIGRP packet is encapsulated in an Ethernet frame,

�the destination MAC address is

8© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

�the destination MAC address isalso a multicast address: 01-00-5E-00-00-0A.

EIGRPEIGRP� All fields are shown to provide an accurate picture of the

EIGRP message format. However, only the fields relevant to the CCNA candidate are discussed.

EIGRP packet header contains� EIGRP packet header contains–Opcode field

•Update•QueryQuery•Reply•Hello

–Autonomous System numberS• The AS number is used to track multiple

instances of EIGRP.

� EIGRP Parameters contains–WeightsWeights

•EIGRP uses for its composite metric. •By default, only bandwidth and delay are weighted. Both are set to 1. •The other K values are set to zero.

–Hold time•The amount of time the EIGRP neighbor receiving this message

9© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

neighbor receiving this messageshould wait before considering the advertising router to be down.

Page 206: Nota CCNA Exp 2 - Routing Protocols and Concepts

EIGRPEIGRP� TLV: IP internal contains (EIGRP routes

within an autonomous system)–Metric field (Delay and Bandwidth)–Metric field (Delay and Bandwidth)

•Delay is calculated as the sum of delays from source to destination in units of 10 microseconds.•Bandwidth is the lowest configured bandwidth gof any interface along the route.

–Subnet mask field•The subnet mask is specified as the prefixlength or the number of network bits in the

b t ksubnet mask.•255.255.255.0 is 24

–Destination field•the address of the destination network.t e add ess o t e dest at o et o•Although only 24 bits are shown in this figure. •If a network address is longer than 24 bits, then the Destination field is extended for another 32 bits

� TLV: IP external contains–Fields used when external

routes are imported into

10© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

EIGRP routing process– import or redistribute a route into EIGRP.

EIGRPEIGRPProtocol Dependent Modules (PDM)

EIGRP PDM t t l� EIGRP uses PDM to route severaldifferent protocols i.e. IP, IPX & AppleTalk

� PDMs are responsible for the specific routing task for each network layerrouting task for each network layerprotocol

–As you can see in the figure, EIGRP uses different EIGRP packets and

i t i t i hb t lmaintains separate neighbor, topology,and routing tables for each Network layer protocol.

•The IP-EIGRP module is responsibleThe IP EIGRP module is responsiblefor sending and receiving EIGRP packets that are encapsulated in IP and for using DUAL to build and maintain the IP routing table. How do people routeg•The IPX EIGRP module is responsible for exchanging routing information about IPX networks with other IPX EIGRP routers

How do people routeIPX or Appletalk today if they still get either IPX A l t lk?

11© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

other IPX EIGRP routers.•Apple-Talk EIGRP is for Apple-talk

IPX or Appletalk?

Page 207: Nota CCNA Exp 2 - Routing Protocols and Concepts

EIGRPEIGRPReliable Transport Protocol (RTP)

P rpose of RTP� Purpose of RTP–Used by EIGRP to transmit and receive EIGRP packets– EIGRP was designed as a Network layerg yindependent routing protocol; therefore, it cannot use the services of UDP or TCP because IPX and Appletalk do not use protocols from the TCP/IP protocol suite.

� Characteristics of RTP–Involves both reliable & unreliable delivery ofEIGRP packet

�Reliable delivery requires acknowledgment�Reliable delivery requires acknowledgmentfrom destination�Unreliable delivery does not require an acknowledgement from destination

P k t b t–Packets can be sent�Unicast�Multicast

–Using address 224 0 0 10

12© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

–Using address 224.0.0.10

EIGRPEIGRPEIGRP’s 5 Packet Types

•Hello•Update•ACK

� Hello packets–Used to discover & form adjacencies with neighbors

ACK•Query•ReplyUsed to discover & form adjacencies with neighbors

–EIGRP hello packets are multicasts and use unreliabledelivery.

13© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 208: Nota CCNA Exp 2 - Routing Protocols and Concepts

EIGRPEIGRP� Update packets

–Update packets are used to propagate

•Hello•Update•ACKUpdate packets are used to propagate

routing information–Update packets are sent only when necessary.

G

ACK•Query•Reply

–EIGRP updates are sent only to those routers that require it. –When a new neighbor is discovered, unicast update packets are sent so that the p pneighbor can build up its topology table. –In other cases, such as a link-cost change, updates are multicast. U d t l t itt d li bl–Updates always are transmitted reliably

� Acknowledgement packets–Used to acknowledge receipt of update,query & reply packets–An acknowledgment packet is a hello packet that has no data. EIGRP acknowledgement packets are

•R2 has lost connectivity to the LAN attached to its FastEthernet interface. •R2 immediately sends an unicast Update to R1 and R3 noting the downed route.

14© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

–EIGRP acknowledgement packets arealways sent as an unreliable unicast

g•R1 and R3 respond with an unicastacknowledgement.

EIGRP

Q & R l k t

•Hello•Update•ACK� Query & Reply packets

�Used by DUAL for searching for networks

ACK•Query•Replynetworks

�Queries and replies use reliable delivery.�Query packets can use

�MulticastR l k t l�Reply packet use only

�unicast•R2 has lost connectivity to the LAN•R2 has lost connectivity to the LANand it sends out queries to all EIGRP neighbors.•All neighbors must send a reply

15© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

regardless of whether or not they have a route to the downed network.

Page 209: Nota CCNA Exp 2 - Routing Protocols and Concepts

EIGRP

Query Update Reply Hello Acknowledge

Reliable Reliable Reliable Unreliable Unreliable(not require acknowledgment )

(a hello packet that has no data )

multicast Multicast & unicast

unicast multicast unicast

16© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

EIGRPEIGRP� Purpose of Hello Protocol

To discover neighbors & establish adjacencies with neighbor routers–To discover neighbors & establish adjacencies with neighbor routers

� Characteristics of hello protocolTime interval for sending hello packet–Time interval for sending hello packet�5 seconds - high bandwidth (greater than T1) �60 seconds - multipoint circuits T1 bandwidth or slower p

-Holdtime�This is the maximum time router should wait before declaring a neighbor down�Default holdtime

–3 times hello interval

17© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

»15 seconds»180 seconds

Page 210: Nota CCNA Exp 2 - Routing Protocols and Concepts

EIGRPEIGRPEIGRP Bounded Updates

� EIGRP only sends update when there is a change in route status

� Partial update–A partial update includes only the route information that has changed – the whole routing table is NOT sent

� Bounded update� Bounded update–When a route changes, only those devices that are impacted will be notified of the change

� EIGRP’s use of partial bounded updates minimizes use of bandwidth

18© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

EIGRPEIGRPDiffusing Update Algorithm (DUAL)Diffusing Update Algorithm (DUAL)

–Purpose•EIGRP’s primary method for preventing routing loops•And also hold-down timers and split horizon, too.

–Advantage of using DUALP id f f t ti b k i li t f l•Provides for fast convergence time by keeping a list of loop-

free backup routes–DUAL maintains a list of backup routes it has already determined to be loop-free. If the primary route in the routing table fails, the best backup route is immediately added to the routing table.

19© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 211: Nota CCNA Exp 2 - Routing Protocols and Concepts

EIGRP

� Administrative Distance (AD)–Defined as the trustworthiness of the source route

� EIGRP default administrative distances–Summary routes = 5Summary routes 5–Internal routes = 90–Imported routes = 170

20© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

EIGRP

A th ti tiAuthentication

� EIGRP canEncrypt routing information– Encrypt routing information

– Authenticate routing information

� It is good practice to authenticateIt is good practice to authenticatetransmitted routing information. – This practice ensures that routers will

only accept routing information fromonly accept routing information fromother routers that have been configured with the same password or authentication information.authentication information.

� Note: Authentication does not encrypt the router's routing table.

21© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

http://www.ciscopress.com/articles/article.asp?p=1171169&seqNum=3

Page 212: Nota CCNA Exp 2 - Routing Protocols and Concepts

EIGRPEIGRPNetwork Topology

� Topology used is the same as previous chapters with the addition of an ISP router

–ISP router does not physically exist

� EIGRP will automatically� EIGRP will automaticallysummarizes at classful boundaries, similar to RIP.

22© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Basic EIGRP ConfigurationBasic EIGRP Configuration� Autonomous System (AS) & Process IDs

–This is a collection of networks under the control of a–This is a collection of networks under the control of asingle authority (reference RFC 1930)–AS Numbers are assigned by IANA

�� ARIN not IANA–Entities needing AS numbers

�ISP�Internet Backbone prodiersInternet Backbone prodiers�Institutions connecting to other institutions using AS numbers�These ISPs and large institutions use the exterior gateway routing protocol or BGP, to propagate routing information.

16-bit and 32-bit AS NumbersCommencing 1 January 2007,"16-bit only AS Numbers" refers to AS numbers in the range 0 - 65535

23© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

16 bit only AS Numbers refers to AS numbers in the range 0 65535"32-bit only AS Numbers" refers to AS Numbers in the range 65,536 - 4,294,967,295"32-bit AS Numbers" refers to AS Numbers in the range 0 - 4,294,967,295

Page 213: Nota CCNA Exp 2 - Routing Protocols and Concepts

Basic EIGRP ConfigurationBasic EIGRP Configuration� EIGRP autonomous system

number actually functions as anumber actually functions as aprocess ID

–The vast majority of companies and institutions with IP networksand institutions with IP networksdo not need an AS number–The ISP is responsible for the

ti f k t ithi itrouting of packets within itsautonomous system and between other autonomous systems.

� Process ID represents an instance of the routing protocol running on a router

� ExampleRouter(config)#router eigrp autonomous-system

24© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Basic EIGRP Configuration

The router eigrp commandThe router eigrp command

� The global command that enables eigrp ist i t trouter eigrp autonomous-system

-All routers in the EIGRP routing domain must use th ID b (the same process ID number (autonomous-systemnumber)

25© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 214: Nota CCNA Exp 2 - Routing Protocols and Concepts

B i EIGRP C fi tiBasic EIGRP ConfigurationThe Network Command

� Functions of the network command–Enables interfaces to transmit & receive EIGRP updates–Includes network or subnet in EIGRP updates

� Examplep–Router(config-router)#network network-address

The network-address is the classful network address for this interface.

a single classful network statement is used on R1 to include both 172.16.1.0/24 and 172.16.3.0/30 subnets:172.16.1.0/24 and 172.16.3.0/30 subnets:

26© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

When EIGRP is configured on R2, DUAL sends a notification message to the console stating that a neighbor relationship with another EIGRP router has been established.

Basic EIGRP ConfigurationBasic EIGRP Configuration� The network Command with a Wildcard Mask

-This option is used when you want to configure EIGRP to advertise specific subnets-Example

Router(config-router)#network network-address [wildcard-mask]

192.168.10.8 – 192.168.10.11

27© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 215: Nota CCNA Exp 2 - Routing Protocols and Concepts

Basic EIGRP ConfigurationBasic EIGRP Configuration� Router(config-router)#network network-address [wildcard-mask]

� Think of a wildcard mask as the inverse of a subnet mask.

� The inverse of subnet mask 255.255.255.252 is 0.0.0.3.

� To calculate the inverse of the subnet mask, subtract the subnet mask from 255.255.255.255:

255.255.255.255

- 255.255.255.252

---------------

0. 0. 0. 3

Wildcard mask

28© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

B i EIGRP C fi tiBasic EIGRP ConfigurationVerifying EIGRP

� EIGRP routers must establish adjacencies with their neighbors before any updates can be sent or receivedg y p

� Command used to view neighbor table and verify that EIGRP has established adjacencies with neighbors isj g

show ip eigrp neighborsH column Lists SRTT (S th R d T i Ti )H column - Liststhe neighbors in the order they were learned.

SRTT (Smooth Round Trip Timer)

Queue Count - Should always be zero.

RTO (Retransmit Interval) - Used by RTP to manage reliableby RTP to manage reliableEIGRP packets.

Sequence Number - Used to track updates, queries, and reply packets.

29© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 216: Nota CCNA Exp 2 - Routing Protocols and Concepts

EIGRP

� The show ip protocols command is also used to verify that EIGRP is enabledenabled

� Remember, the process ID must be , pthe same on all routers for EIGRP to establish neighbor adjacencies and share routing information.

� EIGRP's internal and external administrative distances are also displayed:

–Distance: internal 90 external 170

30© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Basic EIGRP Configuration We willBasic EIGRP ConfigurationExamining the Routing

We willconfigure the bandwidth later.

g gTable

� The show ip routecommand is also used to verify EIGRPverify EIGRP

–EIGRP routes are denoted in a routing table by the letter “D”–EIGRP is a classless

ti t l (i l d throuting protocol (includes thesubnet mask in the routing update), it supports VLSM and CIDR.

� By default EIGRPBy default , EIGRPautomatically summarizes routes at major network boundary

–We can disable the automatic summarization with the no auto-summary command. We will examine this in more detail in a later

31© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

detail in a later.

Page 217: Nota CCNA Exp 2 - Routing Protocols and Concepts

EIGRP Null0 Summary RouteEIGRP Null0 Summary Route� EIGRP has automatically included a summary route to Null0

(192 168 10 0/24 and 172 16 0 0/16)(192.168.10.0/24 and 172.16.0.0/16)–Null0 is not a physical interface–In the routing table summary routes are sourced from Null0

�Reason: routes are used for advertisement purposes–EIGRP will automatically include a null0 summary route as child route when2 conditions are met2 conditions are met

�At least one subnet is learned via EIGRP�Automatic summarization is enabled�If the packet matches the level 1 parent - the classful network address - but none of the subnets, the packet is discarded.

32© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Basic EIGRP Configuration

� R3’s routing table shows that the 172.16.0.0/16 network is automatically summarized byy yR1 & R3

–R1 and R2 are not propagating the individualpropagating the individualsubnets because of automatic summarization.

� [Tony] We will configure the bandwidth later. Once theba d dt ate O ce t ebandwidth is reconfigured, you will not see the equal-cost route on R3.

33© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

route on R3.

Page 218: Nota CCNA Exp 2 - Routing Protocols and Concepts

EIGRP Metric CalculationEIGRP Metric CalculationEIGRP Composite Metric & the K Values

EIGRP th f ll i l i it it t i� EIGRP uses the following values in its composite metric-Bandwidth, delay, reliability, and load (reliability and load are not used)

� The composite metric used by EIGRP� The composite metric used by EIGRP– formula used has values K1 �K5

K1 & K3 = 1K2, K4, K5 = 0

34© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

EIGRP Metric Calculation

U th h i t l d t if th K� Use the sh ip protocols command to verify the Kvalues

Again, changing these values to other than the default is not recommended unless the networkunless the networkadministrator has a very good reason to do so.

35© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 219: Nota CCNA Exp 2 - Routing Protocols and Concepts

EIGRP Metric CalculationEIGRP Metric CalculationEIGRP Metrics

U th h i t f� Use the show interfacescommand to view metrics

� EIGRP Metrics–Bandwidth – EIGRP uses a static bandwidth to calculate metric

Most serial interfaces use–Most serial interfaces usea default bandwidth value of 1.544Mbos (T1)–The value of the b d idthbandwidth may or may not reflect the actual SPEED of the interface. –If actual SPEED of the link differs from the default bandwidth value, then you should modify the bandwidth value,

36© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

The default bandwidth for ethernet is 10,000 Kbits. The default bandwidth for fastethernet is 100,000 Kbits.

EIGRP Metric Calculation

EIGRP MetricsEIGRP Metrics

� Delay is the defined as the measure of time it takes for ameasure of time it takes for apacket to traverse a route

–it is a static value based onit is a static value based onlink type to which interface is connected–The delay value, much like the bandwidth value, is a default value that can be changed by thethat can be changed by thenetwork administrator manually.

37© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 220: Nota CCNA Exp 2 - Routing Protocols and Concepts

EIGRP M t i C l l tiEIGRP Metric Calculation� Reliability (not a default EIGRP metric)

–A measure of the likelihood that a link will fail or how often the link has experienced errors. –Measure dynamically & expressed as a fraction of 255

•the higher the fraction the better the reliability•the higher the fraction the better the reliability–Reliability is calculated on a 5-minute weighted average to avoid the sudden impact of high (or low) error rates.

� Load (not a default EIGRP metric)( )– A number that reflects how much traffic is using a link– Number is determined dynamically and is expressed as a fraction of 255

�The lower the fraction the less the load on the link�This value is calculated on a 5-minute weighted average to avoid the sudden impact of high (or low) channel usage.

38© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

EIGRP Metric CalculationEIGRP Metric CalculationUsing the Bandwidth Commandg

� Modifying the interface bandwidth-Router(config-if)#bandwidth kilobits-Router(config-if)#bandwidth kilobits

� Verifying bandwidth U th h i t f d–Use the show interface command

� Note – bandwidth command doesnot change the link’s physicalnot change the link s physicalbandwidth

–The bandwidth command only modifies the bandwidth metric used byyrouting protocols such as EIGRP and OSPF.

39© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 221: Nota CCNA Exp 2 - Routing Protocols and Concepts

EIGRP Metric CalculationEIGRP Metric Calculation� The EIGRP metric can be determined by examining they g

bandwidth delay

The value before changebefore changethe bandwidth is

2172416

40© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

EIGRP Metric Calculation

� EIGRP uses the lowest bandwidth (BW)in its metric calculation

Calculated BW = reference BW / lowest BW(kbps)

� Delay – EIGRP uses the cumulative sum of all outgoing� Delay – EIGRP uses the cumulative sum of all outgoinginterfaces

Calculated Delay = the sum of outgoing interface delaysCalculated Delay the sum of outgoing interface delays

� EIGRP Metric = calculated BW + calculated delay

41© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 222: Nota CCNA Exp 2 - Routing Protocols and Concepts

EIGRP Metric Calculation

10,000,000 is divided by 1024. If the result is not a whole number, then the value is rounded down. In this case, 10,000,000 divided by 1024 equals 9765.625. The .625 is dropped before multiplying by 256. The bandwidth portion of the composite metric is 2 499 840bandwidth portion of the composite metric is 2,499,840.

42© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

DUAL Concepts

� The Diffusing Update Algorithm (DUAL) is used to prevent loopingp p g

–Successor–Feasible Distance (FD)–Feasible Successor (FS)–Reported Distance (RD) or Advertised Distance (AD)–Feasible Condition or Feasibility Condition (FC)

43© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 223: Nota CCNA Exp 2 - Routing Protocols and Concepts

DUAL ConceptsDUAL Concepts� Successor

The best least cost routeto a destination found in the routing tablethe routing table

� Feasible distanceThe lowest calculatedThe lowest calculatedmetric along a path to a destination network

� 2 commands can be used to find the “successor” and “feasiblesuccessor and feasibledistance”:

–show ip route

44© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

–show ip eigrp topology

DUAL ConceptsDUAL Concepts

� EIGRP� EIGRPTopologyTableTabledissected

45© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 224: Nota CCNA Exp 2 - Routing Protocols and Concepts

DUAL ConceptsDUAL ConceptsFeasible Successors, Feasibility Condition & Reported

Distance� Feasible Successor

–This is a loop free backup route to the same destination as successor route–If the link between R2 and–If the link between R2 andR3 failed, the R1 will become the successor for sending traffic to 192 168 1 0traffic to 192.168.1.0

46© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

EIGRP technologies (cont )EIGRP technologies (cont.)Feasible Successor, FC: RD30 < FD31

172 30 1 0172.30.1.0

FD to 172.30.1.0 is 31 via Router Y

Ad i d

Current Successor = 31 RD of RTY= 21

RTZ is NOT FeasibleSuccessor, FC: RD220 not< FD31

Advertised orDestination Feasible Dist. Reported. Dist. Neighbor172.30.1.0 40 30 X In Topology Table

47© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

172.30.1.0 31 21 Y In Routing Table172.30.1.0 230 220 Z Not in Topology Table

Page 225: Nota CCNA Exp 2 - Routing Protocols and Concepts

Verifying basic EIGRPVerifying basic EIGRP

48© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Verifying basic EIGRPVerifying basic EIGRP

49© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 226: Nota CCNA Exp 2 - Routing Protocols and Concepts

What if the successor fails?1) If feasible successor exists:

What if the successor fails?

� If current successor route fails, feasible successor becomes the current successor, i.e. the current route.

� Routing of packets continue with little delay.g p y

2) If no feasible successor exists:

� This may be because the Reported Distance is greater than the Feasible Distance.

B f thi t b i t ll d it t b l d i th ti t t d� Before this route can be installed, it must be placed in the active state andrecomputed.

� Routing of packets continue but with more of a delay.

50© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

DUAL Concepts

� Feasibility Condition (FC)–Met when a neighbor’s reported distance (RD) is less than the local router’sthan the local router sFD to the same destination network

Th t d di t i–The reported distance issimply an EIGRP neighbor's feasible distance to the same destination networksame destination network.–The reported distance is the metric that a router reports to a neighbor about

51© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

reports to a neighbor aboutits own cost to that network.

Page 227: Nota CCNA Exp 2 - Routing Protocols and Concepts

DUAL ConceptsDUAL Concepts� Reported distance (RD)

The metric that a router–The metric that a routerreports to a neighbor about its own cost to that network–R2 examines the reportedR2 examines the reporteddistance (RD) of 2172416 from R1. Because the reported distance (RD) of R1 is less than R2's own feasible distance (FD)( )of 3014400, R1 meets the feasibility condition. R1 is now a feasible successor for R2 to the 192.168.1.0/24 network.

� Why isn't R1 the successor if its reported distance (RD) is less than R2's feasible distance (FD) t 192 168 1 0/24?to 192.168.1.0/24?

–Because the total cost for R2, its feasible distance (FD), to reach 192 168 1 0/24 is greater

52© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

reach 192.168.1.0/24 is greaterthrough R1 than it is through R3.

DUAL ConceptsDUAL Concepts

� EIGRP Topology table� EIGRP Topology table–Viewed using the show ip

eigrp topology command�Contents of table include:

– all successor routes– all feasible successor

routes

53© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 228: Nota CCNA Exp 2 - Routing Protocols and Concepts

DUAL ConceptsDUAL Concepts

� EIGRP Topology� EIGRP TopologyTable dissected

P - This route is in theP This route is in thepassive state. When DUAL is not performing its diffusing computations to d t i th fdetermine a path for a network, the route will be in a stable mode, known as the passive statethe passive state.A - If DUAL is recalculating or searching for a new path, the route will be in an

ti t tactive state.

All routes in the topology table should be in the

54© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

table should be in thepassive state for a stable routing domain.

if there is not a second entry, then there are no feasible successors

DUAL ConceptsDUAL Concepts

� To view detailed� To view detailedinformation about the metrics of a specific entry in the topology table, add the optional parameter [network] toparameter [network] tothe show ip eigrp topology command

� Remember that EIGRP is a distance vector routing protocol.

55© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 229: Nota CCNA Exp 2 - Routing Protocols and Concepts

DUAL ConceptsDUAL ConceptsTopology Table: No Feasible

SuccessorSuccessor

� The topology table for R1 to the network 192.168.1.0 only shows theet o 9 68 0 o y s o s t esuccessor 192.168.10.6. There are no feasible successors.

By looking at the actual physical–By looking at the actual physicaltopology or network diagram, it is obvious that there is a backup route to 192.168.1.0/24 through R2.to 192.168.1.0/24 through R2.

� Why isn't R2 listed as a feasible successor?

–R2 is not a feasible successor because it does not meet the feasibility condition.

56© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

DUAL ConceptsDUAL ConceptsNo Feasible Successor

show ip eigrp topology all-links

� Looking at the topology it is obvious that R2 is a backup routeR2 is a backup route,

–The command shows all possible paths to a network including successors, feasible successors and even thosefeasible successors, and even thoseroutes that are not feasible successors.–For R2 to be considered a feasible successor it must meet the feasibilitysuccessor, it must meet the feasibilitycondition. R2's feasible distance to reach 192.168.1.0/24 must be less the R1's current feasible distance (FD) As we cancurrent feasible distance (FD). As we cansee in the figure, R2's feasible distance is 3014400, which is higher than R1's feasible distance of 2172416.

57© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 230: Nota CCNA Exp 2 - Routing Protocols and Concepts

DUAL ConceptsDUAL Concepts� Does this mean R2 cannot be

used if the successor fails?–No, R3 can be used, but there will be a longer delay before adding it tobe a longer delay before adding it tothe routing table. –Before this can happen, DUAL will need to do some further processing.

58© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

DUAL Concepts

� The centerpiece of EIGRP is DUAL d it EIGRP t l l tiand its EIGRP route-calculation

engine. The actual name of this technology is DUAL Finite State Machine (FSM).Machine (FSM).

� Finite Sate Machine (FSM)–An abstract machine that defines a set of possible states somethinga set of possible states somethingcan go through, what event causes those states and what events result form those states–FSMs are used to describe how a device, computer program, or routing algorithm will react to a set of input eventsof input events–Selects a best loop-free path to a destination

Selects alternate routes by using

59© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

–Selects alternate routes by usinginformation in EIGRP tables

Page 231: Nota CCNA Exp 2 - Routing Protocols and Concepts

DUAL ConceptsFinite State Machines (FSM)Finite State Machines (FSM)

� To examine output from EIGRP’s finite state machine us the debug eigrp fsm commandus the debug eigrp fsm command

60© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

More EIGRP ConfigurationsThe Null0 Summary Route

� By default, EIGRP uses the Null0 interface to discard any packets that match the parent route but do not match any of the child routes

� EIGRP automatically includes a null0 summary route as a child route whenever both of the following conditions exist

–One or subnets exists that was learned via EIGRPOne or subnets exists that was learned via EIGRP–Automatic summarization is enabled

61© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 232: Nota CCNA Exp 2 - Routing Protocols and Concepts

More EIGRP ConfigurationsMore EIGRP Configurations� Regardless of whether classful or classless

routing behavior is being used the null0routing behavior is being used, the null0summary will potentially be used and denying the use of any supernet or default routeroute.

� Disabling Automatic Summarization–The no auto-summary command is usedThe no auto-summary command is usedto disable automatic summarization

•This causes all EIGRP neighbors to send updates that will not besend updates that will not beautomatically summarized

�this will cause changes in both g-routing tables -topology tables

62© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

More EIGRP ConfigurationsMore EIGRP Configurations� The no auto-summary command

63© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 233: Nota CCNA Exp 2 - Routing Protocols and Concepts

More EIGRP ConfigurationsMore EIGRP Configurations� The no auto-summary command

Witho t a tomatic s mmari ation R3's� Without automatic summarization, R3'srouting table now includes the three subnets, 172.16.1.0/24, 172.16.2.0/24, and 172.16.3.0/24. Why does R3's routing table y gnow have two equal cost paths to 172.16.3.0/24? Shouldn't the best path only be through R1 with the 1544 Mbps link?

Remember that EIGRP only uses the link with–Remember that EIGRP only uses the link withthe slowest bandwidth when calculating the composite metric. –The slowest link is the 64 Kbps link that contains the 192.168.3.0/24 network. In this example, the 1544 Mbps link and the 1024 Kbps link are irrelevant in the calculation as far as the bandwidth metric is concerned. –Because both paths have the same number and types of outgoing interfaces, the delay values end up being the same. As a result the EIGRP metric for both paths is

64© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

–As a result, the EIGRP metric for both paths isthe same, even though the path through R1 would actually be the "faster" path.

M l S i iManual Summarization� EIGRP can be configured to

summarize routes, whether or not automatic summarization (auto-summary) is enabled.

–EIGRP is a classless routing protocol & include subnet mask in updatep

� Command used to configure manual summarization

–Router(config-if)#ipsummary-address eigrp as-number network-address

b t ksubnet-mask

65© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 234: Nota CCNA Exp 2 - Routing Protocols and Concepts

More EIGRP Configurations

EIGRP Default RoutesEIGRP Default Routes

� “quad zero” static default routeCan be used with any currently-Can be used with any currently

supported routing protocol-Is usually configured on a router that is connected a network outside the EIGRP domain (for example, to an ISP. )

� EIGRP & the “Quad zero” static default route� EIGRP & the Quad zero static default route–Requires the use of the redistributestatic command to include the static default route in EIGRP routing updates to other routers.

66© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

More EIGRP Configurations

� In the routing tables for R1In the routing tables for R1and R3, notice the routing source and administrative distance for the new static default route. The entry for the static default route on R1the static default route on R1is the following:

� D*EX 0.0.0.0/0 [170/3651840][ ]via 192.168.10.6, 00:01:08, Serial0/1

–D: This static route was learned from an EIGRP routing updaterouting update.–*: The route is a candidate for a default route.–EX: The route is an external EIGRP route in this case aEIGRP route, in this case astatic route outside of the EIGRP routing domain.–170: This is the administrative distance of an external EIGRP route

67© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

external EIGRP route.

Page 235: Nota CCNA Exp 2 - Routing Protocols and Concepts

Fi T i EIGRPFine-Tuning EIGRP� EIGRP bandwidth utilization

–By default, EIGRP uses only up to 50% of interface bandwidth for EIGRP information

Thi t th EIGRP f tili i li k d t•This prevents the EIGRP process from over-utilizing a link and notallowing enough bandwidth for the routing of normal traffic.

–The command to change the percentage of bandwidth used by EIGRP is

Router(config-if)#ip bandwidth-percent eigrp as-number percentnumber percent

In our example, we are limiting EIGRP to no more than 50

t f th li k' b d idthpercent of the link's bandwidth.Therefore, EIGRP will never use more the 32kbps of the link's bandwidth for EIGRP packet

68© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

bandwidth for EIGRP packettraffic.

More EIGRP ConfigurationsMore EIGRP Configurations� Configuring Hello Intervals and Hold Times

Hello inter als and hold times are config rable on a per interface-Hello intervals and hold times are configurable on a per-interfacebasis-The command to configure hello interval is

Router(config-if)#ip hello-interval eigrp as-number seconds

� Changing the hello interval also requires changing the hold time to a value greater than or equal to the hello interval

-The command to configure hold time value isRouter(config-if)#ip hold-time eigrp as-number seconds

DefaultsFor low-speed, NBMA networks: 60 seconds F ll th t k 5 dFor all other networks: 5 seconds

Defaults

69© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

For low-speed, NBMA networks: 180 seconds For all other networks: 15 seconds

Page 236: Nota CCNA Exp 2 - Routing Protocols and Concepts

SummarySummary� Background & History

EIGRP is a derivative of IGRP–EIGRP is a derivative of IGRP�EIGRP is a Cisco proprietary distance vector routing protocol released in 1994

� EIGRP terms and characteristics–EIGPR uses RTP to transmit & receive EIGRP packetsp–EIGRP has 5 packet type:

�Hello packets�Update packets�Acknowledgement packets�Query packets�Reply packets

70© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

–Supports VLSM & CIDR

Summary

� EIGRP terms and characteristicsEIGRP uses a hello protocol–EIGRP uses a hello protocol�Purpose of hello protocol is to discover & establish adjacenciesj

–EIGRP routing updates�AperiodicAperiodic�Partial and bounded�Fast convergenceFast convergence

71© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 237: Nota CCNA Exp 2 - Routing Protocols and Concepts

Summary

� EIGRP commands–The following commands are used for EIGRPThe following commands are used for EIGRPconfiguration

�RtrA(config)#router eigrp [autonomous-system #]�RtrA(config-router)#network network-number

–The following commands can be used to verify EIGRPSh i l�Show ip protocols

�Show ip eigrp neighborsSho ip ro te�Show ip route

72© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Summary

� EIGRP metrics includeBandwidth (default)–Bandwidth (default)

–Delay (default)R li bili–Reliability

–Load

73© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 238: Nota CCNA Exp 2 - Routing Protocols and Concepts

SummarySummary� DUAL

P f DUAL–Purpose of DUAL�To prevent routing loops

–Successor�Primary route to a destination

–Feasible successor�Backup route to a destination

–Feasible distance�Lowest calculated metric to a destination

–Reported distance�The distance towards a destination as advertised b t i hb

74© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

by an upstream neighbor

SummarySummary� Choosing the best route

Aft t h i d ll d t f di tl–After router has received all updates from directlyconnected neighbors, it can calculate its DUAL

1st metric is calculated for each route�1st metric is calculated for each route�2nd route with lowest metric is designated successor & is placed in routing tablesuccessor & is placed in routing table�3rd feasible successor is found

C i i f f ibl i h–Criteria for feasible successor: it must havelower reported distance to the destination than the installed route’s feasible distancethe installed route s feasible distance–Feasible routes are maintained in topology table

75© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

table

Page 239: Nota CCNA Exp 2 - Routing Protocols and Concepts

Summary

� Automatic summarizationOn by default–On by default

–Summarizes routes on classful boundaryS i i b di bl d i h f ll i–Summarization can be disabled using the following

commandRt A( fi if)# t�RtrA(config-if)#no auto-summary

76© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Link-State Routing Protocols

Chapter 10: Routing Protocols and ConceptsModified by Hasimi Sallehudin

1© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 240: Nota CCNA Exp 2 - Routing Protocols and Concepts

Objectives

� Describe the basic features & concepts of link-state prouting protocols.– Distance vector routing protocols are like road signs

because routers must make preferred path decisions basedbecause routers must make preferred path decisions basedon a distance or metric to a network.

– Link-state routing protocols are more like a road map because they create a topological map of the network andbecause they create a topological map of the network andeach router uses this map to determine the shortest path to each network.The ultimate objective is that every router receives all of the– The ultimate objective is that every router receives all of thelink-state information about all other routers in the routing area. With this link-state information, each router can create its own topological map of the network and independentlyits own topological map of the network and independentlycalculate the shortest path to every network.

� List the benefits and requirements of link-state routing

2© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

protocols.

Link-State Routing

� Link state routing protocols� Link state routing protocols-Also known as shortest path first algorithms

-These protocols built around Dijkstra’s SPF

OSPF ill b di d i Ch t 11 d IS IS ill b di d i CCNP

3© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

OSPF will be discussed in Chapter 11, and IS-IS will be discussed in CCNP.

Page 241: Nota CCNA Exp 2 - Routing Protocols and Concepts

Link-State Routing

� Dikjstra’s algorithm also known as the shortest path first (SPF) algorithm

Thi l ith l t t l h th f–This algorithm accumulates costs along each path, fromsource to destination.

4© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Link-State Routing

� The shortest path to a destination is not necessarily the path with the least number of hops

5© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 242: Nota CCNA Exp 2 - Routing Protocols and Concepts

Link-State Routing Process� How routers using Link State Routing Protocols reach convergence

1 Each routers learns about its own directly connected networks1. Each routers learns about its own directly connected networks– interface is in the up state

2. Each router is responsible for meeting its neighbors on directly t d t kconnected networks

– exchange hello packet to other directly connected link state routers.3. Each router builds a Link-State Packet (LSP) containing the state of ( ) g

each directly connected link – recording all the pertinent information about each neighbor, including

neighbor ID, link type, and bandwidth.4. Each router floods the LSP to all neighbors, who then store all LSPs

received in a database.– Each router stores a copy of each LSP received from its neighbors in

a local databasea local database.5. Each router uses the database to construct a complete map of the

topology and computes the best path to each destination network.Th SPF l ith i d t t t th f th t l d

6© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

– The SPF algorithm is used to construct the map of the topology andto determine the best path to each network.

Link-State Routing: Step 1 – Learn about directly connected Networks

� Link

This is an interface on as s a te ace o arouter

� Link stateLink state

This is the information about the state of theabout the state of thelinks

7© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 243: Nota CCNA Exp 2 - Routing Protocols and Concepts

Link-State Routing: step 2 - Sending Hello Packets to Neighbors

� Link state routing protocols use a hello protocol� Link state routing protocols use a hello protocolPurpose of a hello protocol:

T di i hb (th t th-To discover neighbors (that use the same link state routing protocol) on its link

8© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Link-State Routing:

� Connected interfaces that are

Link-State Routing:step 2 - Sending Hello Packets to Neighbors

� Connected interfaces that areusing the same link state routing protocols will exchangerouting protocols will exchangehello packets.

� Once routers learn it has� Once routers learn it hasneighbors they form an adjacencyadjace cy

– 2 adjacent neighbors will exchange hello packets – These packets will serve as a keep alive function

9© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 244: Nota CCNA Exp 2 - Routing Protocols and Concepts

Link-State Routing:

� Contents of LSP:

Link-State Routing:step 3 - Building the Link State Packet (LSP)

� Contents of LSP:– State of each directly connected link– Includes information about neighbors such as neighbor ID linkneighbors such as neighbor ID, linktype, & bandwidth.

� A simplified version of the LSPs from R1 is:

1. R1; Ethernet network 10.1.0.0/16; Cost 22. R1 -> R2; Serial point-to-point network; 10.2.0.0/16; Cost 203. R1 -> R3; Serial point-to-point network; 10.3.0.0/16; Cost 54. R1 -> R4; Serial point-to-point

/ C

10© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

network; 10.4.0.0/16; Cost 20

Link-State Routing:

� Once LSP are created they are

Link-State Routing:step 4 - Flooding LSPs to Neighbors

� Once LSP are created they areforwarded out to neighbors.

–Each router floods its link-stateac ou e oods s s a einformation to all other link-state routers in the routing area.

Whenever a router receives an LSP–Whenever a router receives an LSPfrom a neighboring router, it immediately sends that LSP out all other interfaces except the interfaceother interfaces except the interfacethat received the LSP. –This process creates a flooding effect p gof LSPs from all routers throughout the routing area.

11© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 245: Nota CCNA Exp 2 - Routing Protocols and Concepts

Link-State Routing:

LSP t t d th f ll i diti

Link-State Routing:step 4 - Flooding LSPs to Neighbors� LSPs are sent out under the following conditions

– Initial router start up or routing processWh th i h i t l– When there is a change in topology• including a link going down or coming up, or a neighbor adjacency being established or brokenj y g

12© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Link-State Routing:

� Routers use a database to

Link-State Routing:step 5 - Constructing a link state data base

� Routers use a database toconstruct a topology map of the network

–After each router has propagated its own LSPs using the link-state flooding process each router willflooding process, each router willthen have an LSP from every link-state router in the routing area. –These LSPs are stored in the link-state database. –Each router in the routing area canEach router in the routing area cannow use the SPF algorithm to construct the SPF trees that you saw earlier

13© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

earlier.

Page 246: Nota CCNA Exp 2 - Routing Protocols and Concepts

Link-State Routing:Link-State Routing:step 5 - Constructing a link state data base

router R1 has learned the link-state information for each router in its routing area.routing area.

With a complete link-state database, R1 pcan now use the database and the shortest path first (SPF) algorithm to calculate the preferred path or shortest path to each network.p

14© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Link-State Routing:

� Process begins by examining R2’s LSP information

Link-State Routing:Example - How R1 constructs its SPF tree.

Process begins by examining R2 s LSP information–R1 can ignore the first LSP, because R1 already knows that it is connected to R2 on network 10.2.0.0/16 with a cost of 20.

R1 th d LSP d t li k f R2 t th–R1 can use the second LSP and create a link from R2 to anotherrouter, R5, with the network 10.9.0.0/16 and a cost of 10. This information is added to the SPF tree.

Using the third LSP R1 has learned that R2 has a network–Using the third LSP, R1 has learned that R2 has a network10.5.0.0/16 with a cost of 2 and with no neighbors. This link is added to R1's SPF tree.

15© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 247: Nota CCNA Exp 2 - Routing Protocols and Concepts

Link-State Routing:

� Process begins by examining R3’s LSP information

Link-State Routing:Example - How R1 constructs its SPF tree.

Process begins by examining R3 s LSP information–R1 can ignore the first LSP, because R1 already knows that it is connected to R3 on network 10.3.0.0/16 with a cost of 5.

R1 th d LSP d t li k f R3 t th–R1 can use the second LSP and create a link from R3 to therouter R4, with the network 10.7.0.0/16 and a cost of 10. This information is added to the SPF tree.

Using the third LSP R1 has learned that R3 has a network–Using the third LSP, R1 has learned that R3 has a network10.6.0.0/16 with a cost of 2 and with no neighbors. This link is added to R1's SPF tree.

16© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Link-State Routing:

� Process begins by examining R4’s LSP information

Link-State Routing:Example - How R1 constructs its SPF tree.

Process begins by examining R4 s LSP information–R1 can ignore the first LSP because R1 already knows that it is connected to R4 on network 10.4.0.0/16 with a cost of 20. –R1 can also ignore the second LSP because SPF has already learnedR1 can also ignore the second LSP because SPF has already learnedabout the network 10.6.0.0/16 with a cost of 10 from R3. –However, R1 can use the third LSP to create a link from R4 to the router R5, with the network 10.10.0.0/16 and a cost of 10. This information is

dd d t th SPF tadded to the SPF tree.–Using the fourth LSP, R1 learns that R4 has a network 10.8.0.0/16 with a cost of 2 and with no neighbors. This link is added to R1's SPF tree.

17© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 248: Nota CCNA Exp 2 - Routing Protocols and Concepts

Link-State Routing:

� Process begins by examining R5’s LSP information

Link-State Routing:Example - How R1 constructs its SPF tree.

Process begins by examining R5 s LSP information–R1 can ignore the first two LSPs (for the networks 10.9.0.0/16 and 10.10.0.0/16), because SPF has already learned about these links and added them to the SPF tree. –R1 can process the third LSP learning that R5 has a network 10.11.0.0/16 with a cost of 2 and with no neighbors. This link is added to the SPF tree for R1.

18© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Link-State Routing

� Determining the shortest pathDetermining the shortest path–The shortest path to a destination determined by adding the costs & finding the lowest cost

•Network 10.5.0.0/16 via R2 serial 0/0/0 at a cost of 22•Network 10.6.0.0/16 via R3 serial 0/0/1 at a cost of 7at a cost of 7•Network 10.7.0.0/16 via R3 serial 0/0/1 at a cost of 15•Network 10.8.0.0/16 via R3 serial 0/0/1 at a cost of 17•Network 10.9.0.0/16 via R2 serial 0/0/0 at a cost of 30N t k 10 10 0 0/16 i R3 i l 0/0/1•Network 10.10.0.0/16 via R3 serial 0/0/1

at a cost of 25•Network 10.11.0.0/16 via R3 serial 0/0/1 at a cost of 27

Only the LANs are shown in the table, but SPF can also be used to determine the

19© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

used to determine theshortest path to each WAN link network.

Page 249: Nota CCNA Exp 2 - Routing Protocols and Concepts

Link-State Routing

O th SPF l ith h� Once the SPF algorithm hasdetermined the shortest path routes, these routes are placed inroutes, these routes are placed inthe routing table.

� The routing table will also includeThe routing table will also includeall directly connected networks and routes from any other sources, such as static routes. Packets will now be forwarded according to these entries in theaccording to these entries in therouting table.

20© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Link-State Routing Protocols

Advantages of a Link State Routing ProtocolAdvantages of a Link-State Routing Protocol

Routingprotocol

BuildsTopological

map

Router can independentlydetermine the shortest path

ConvergenceEvent driven

routingupdates

Useof

LSP

to every network.

Distance No No Slow Generally No NoDistancevector

No No Slow Generally No No

Link State Yes Yes Fast Generally Yes Yes

21© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 250: Nota CCNA Exp 2 - Routing Protocols and Concepts

Link-State Routing Protocols

� There are several advantages of link-state routing protocols compared to distance vector routing t lprotocols.

� Builds a Topological Map• Link-state routing protocols create a topological map, or SPF tree of the network topology.

•Using the SPF tree each router can independently determine the shortest path to every networkUsing the SPF tree, each router can independently determine the shortest path to every network.• Distance vector routing protocols do not have a topological map of the network.

•Routers implementing a distance vector routing protocol only have a list of networks, which includes the cost (distance) and next-hop routers (direction) to those networks.

� Fast Convergence• When receiving a Link-state Packet (LSP), link-state routing protocols immediately flood the LSP out all

interfaces except for the interface from which the LSP was received. • A router using a distance vector routing protocol needs to process each routing update and update its

ti t bl b f fl di th t th i t f ith t i d d trouting table before flooding them out other interfaces, even with triggered updates.

� Event-driven Updates• After the initial flooding of LSPs, link-state routing protocols only send out an LSP when there is a change

in the topology. The LSP contains only the information regarding the affected link. • Unlike some distance vector routing protocols, link-state routing protocols do not send periodic updates.

� Hierarchical Design• Link-state routing protocols such as OSPF and IS-IS use the concept of areas. Multiple areas create a

hierarchical design to networks allowing for better route aggregation (summarization) and the isolation of

22© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

hierarchical design to networks, allowing for better route aggregation (summarization) and the isolation ofrouting issues within an area.

Link-State Routing Protocols

R i t f i li k t t ti t lRequirements for using a link state routing protocol� Memory requirements

T i ll li k t t ti t l– Typically link state routing protocols use more memory

� Processing RequirementsM CPU i i i d f li k t t ti– More CPU processing is required of link state routing

protocols

� Bandwidth Requirementsq– Initial startup of link state routing protocols can consume lots of bandwidth

This should only occur during initial startup of routers but can– This should only occur during initial startup of routers, but canalso be an issue on unstable networks.

23© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 251: Nota CCNA Exp 2 - Routing Protocols and Concepts

Link-State Routing Protocols� Modern link-state routing protocols are designed to

i i i h ff CPU dminimize the effects on memory, CPU, andbandwidth.

• The use and configuration of multiple areas can reduce the size of the link-state databases. Multiple areas canthe size of the link state databases. Multiple areas canalso limit the amount of link-state information flooding in a routing domain and send LSPs only to those routers that need them.

• For example when there is a change in the topologyFor example, when there is a change in the topology,only those routers in the affected area receive the LSP and run the SPF algorithm.

• This can help isolate an unstable link to a specific area in the routing domainin the routing domain.

� In the figure, If a network in Area 51 goes down, the LSP with the information about this downed link is only flooded to other routers in that area.only flooded to other routers in that area.

• Routers in other areas will learn that this route is down, but this will be done with a type of link-state packet that does not cause them to rerun their SPF algorithm.

Note: Multiple areas with OSPF and IS-IS

24© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

are discussed in CCNP

Link-State Routing Protocols

� 2 link state routing protocols used for routing IP� 2 link state routing protocols used for routing IP-Open Shortest Path First (OSPF)-Intermediate System-Intermediate System (IS-IS)

25© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 252: Nota CCNA Exp 2 - Routing Protocols and Concepts

Summary

� Link State Routing protocols are also known as Shortest Path First protocols

� Summarizing the link state process-Routers 1ST learn of directly connected networksRouters 1ST learn of directly connected networks-Routers then say “hello” to neighbors-Routers then build link state packets-Routers then build link state packets-Routers then flood LSPs to all neighborsRouters use LSP database to build a network topology-Routers use LSP database to build a network topology

map & calculate the best path to each destination

26© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Summary

� LinkAn interface on the routerAn interface on the router

� Link StateInformation about an interface such asInformation about an interface such as

-IP addressSubnet mask-Subnet mask

-Type of networkC t i t d ith li k-Cost associated with link

-Neighboring routers on the link

27© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 253: Nota CCNA Exp 2 - Routing Protocols and Concepts

Summary

� Link State Packets

Aft i iti l fl di dditi l LSP t tAfter initial flooding, additional LSP are sent outwhen a change in topology occurs

� Examples of link state routing protocols

-Open shortest path first

-IS-IS-IS-IS

28© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

OSPF (Single Area OSPF)

Chapter 11: Routing Protocols and Concepts

Modified by Hasimi Sallehudin

1© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 254: Nota CCNA Exp 2 - Routing Protocols and Concepts

Introduction

•In this chapter, you will learn basic, single-area OSPF implementationsand configurations

2© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

and configurations.•More complex OSPF configurations and concepts (multi-areas OSPF)are reserved for CCNP-level courses.

Introduction to OSPFIntroduction to OSPFBackground of OSPF� Began in 1987� 1989 OSPFv1 released in RFC 1131

This version was experimental & never deployed� 1991 OSPFv2 released in RFC 1247� 1998 OSPFv2 updated in RFC 2328� 1999 OSPFv3 published in RFC 2740 p

3© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 255: Nota CCNA Exp 2 - Routing Protocols and Concepts

Introduction to OSPFIntroduction to OSPFOSPF Message Encapsulation� OSPF packet typeOSPF packet type

– There exist 5 types (next slide)

� OSPF packet header –Contains - Router ID an area IDand Type code for OSPF packet type

� IP packet header– Contains - Source IP address, Destination IP address, & Protocoles a o add ess, & o ocofield set to 89. the destination address is set to one of two multicast addresses: 224.0.0.5 or224 0 0 6224.0.0.6.

� Data Link Frame Header –Contains - destination MAC address is

4© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

also a multicast address: 01-00-5E-00-00-05 or 01-00-5E-00-00-06.

I t d ti t OSPFIntroduction to OSPF5 OSPF Packet Types:

� 1. Hello - Hello packets are used to establish and maintain adjacency with other OSPF routers.

� 2. DBD - The Database Description (DBD) packet contains an abbre iated list of the sending ro ter'scontains an abbreviated list of the sending router'slink-state database and is used by receiving routers to check against the local link-state database.

� 3. LSR - Receiving routers can then request more information about any entry in the DBD by sending a Link-State Request (LSR).

� 4. LSU - Link-State Update (LSU) packets are used to reply to LSRs as well as to announce new information.

–LSUs contain 7 different types of Link-State Advertisements (LSAs).–LSUs and LSAs are discussed in a later topic.

5 LSA k Wh LSU i i d th t

5© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

� 5. LSAck - When an LSU is received, the routersends a Link-State Acknowledgement (LSAck) to confirm receipt of the LSU.

Page 256: Nota CCNA Exp 2 - Routing Protocols and Concepts

OSPF: Hello ProtocolOSPF: Hello Protocol� Purpose of Hello Packet

� Discover OSPF neighbors & establish adjacencies� Discover OSPF neighbors & establish adjacencies� Advertise parameters on which routers must agree to become neighbors� Used by multi-access networks to elect a Designated Router and a Backup Designated Router

� Type: OSPF Packet Type: Hello (1), DD (2), LS Request (3), LS Update (4), LS ACK (5)

� Router ID: ID of the originating router

� Area ID: area from which the packet originated

� Network Mask: Subnet mask associated with the sending interfacesending interface

� Hello Interval: number of seconds between the sending router's hellos

� Router Priority: Used in DR/BDR election (discussed l t )later)

� Designated Router (DR): Router ID of the DR, if any

� Backup Designated Router (BDR): Router ID of the BDR, if any

6© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

� List of Neighbors: lists the OSPF Router ID of the neighboring router(s)

OSPF: Hello ProtocolOSPF: Hello Protocol� Establish adjacencies:

– They must agree on three values: Hello Why 10 second hello interval

Also need to have the same Area ID.

y ginterval, Dead interval, and network type.

� OSPF Hello Intervals–Hello interval indicates how often an OSPF router transmits its Hello packets

Why 10 second hello intervalcommunications consider better than the 30 second routing update for RIP?

router transmits its Hello packets–Usually multicast (224.0.0.5) for ALLSPFRouters–sent every 10 seconds on multiaccess and ypoint-to-point segments–Sent every 30 seconds for NBMA segments

� OSPF Dead Intervals–This is the time that must transpire before the neighbor is considered down–Default time is 4 times the hello interval–For multiaccess and point-to-point segmentsFor multiaccess and point to point segments,this period is 40 seconds. –For NBMA networks, the Dead interval is 120 seconds.If the Dead interval expires before the routers

7© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

–If the Dead interval expires before the routersreceive a Hello packet, OSPF will remove that neighbor from its link-state database.

Page 257: Nota CCNA Exp 2 - Routing Protocols and Concepts

OSPF: Hello Protocol

� To reduce the amount of OSPF traffic onTo reduce the amount of OSPF traffic onmultiaccess networks, OSPF elects a Designated Router (DR) and Backup Designated Router (BDR).g ( )

� Hello protocol packets contain information that is used in electing DR and BDR

The DR is responsible for updating all other–The DR is responsible for updating all otherOSPF routers (called DROthers) when a change occurs in the multiaccess network. –The BDR monitors the DR and takes over asThe BDR monitors the DR and takes over asDR if the current DR fails.

� In the figure, R1, R2, and R3 are connected through point to point links Therefore no More detail discussionthrough point-to-point links. Therefore, noDR/BDR election occurs.

–The DR/BDR election and processes will be discussed in a later topic and the topology will

More detail discussionon the DR, BDR, DROther later. You need to know this for

8© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

discussed in a later topic and the topology willbe changed to a multiaccess network.

need to know this forCCNA exam.

Introduction to OSPFIntroduction to OSPFOSPF Link-state Updates� Purpose of a Link State Update (LSU)Purpose of a Link State Update (LSU)

–Used to deliver link state advertisements� Purpose of a Link State Advertisement (LSA)

–Contains information about neighbors & path costs–An LSU packet can contain 11 different types of LSAs,

9© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 258: Nota CCNA Exp 2 - Routing Protocols and Concepts

Introduction to OSPFIntroduction to OSPFOSPF Algorithm

� OSPF routers build & maintain link-stated t b t i i LSAdatabase containing LSAreceived from other routersrouters1. Information found in

database is utilized upon e ec tion of Dijkstra SPFexecution of Dijkstra SPFalgorithm

2. SPF algorithm used to gcreate SPF tree

3. SPF tree used to populate routing table

10© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

routing table

Introduction to OSPFIntroduction to OSPFAdministrative DistanceAdministrative Distance

� Default Administrative Distance for OSPF is 110

11© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 259: Nota CCNA Exp 2 - Routing Protocols and Concepts

Introduction to OSPFIntroduction to OSPF� OSPF Authentication

–It is good practice to authenticate transmittedIt is good practice to authenticate transmittedrouting information. –This is an interface specific configurationp g–This practice ensures that routers will only accept routing information from other routers that have been configured with the same password or authenticationconfigured with the same password or authenticationinformation

MD5 authentication k ID th t

Note: Authentication does not encrypt the router's routing table

uses a key ID thatallows the router to reference multiple passwords, making

?router s routing table. p , g

password migration easier and more secure.

12© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

?

Basic OSPF Configuration

Lab TopologyLab Topology

� Topology used for this chapter –Discontiguous IP addressing scheme–Since OSPF is a classless routing protocol the subnet mask is will be configured as part of ouris will be configured as part of ourOSPF configuration.

13© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 260: Nota CCNA Exp 2 - Routing Protocols and Concepts

Basic OSPF ConfigurationBasic OSPF ConfigurationThe router ospf commandThe router ospf command� To enable OSPF on a router use the following

commandR1(config)#router ospf process-idProcess id

ID cannot be 0

� A locally significant number between 1 and 65535

14© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Basic OSPF ConfigurationBasic OSPF Configuration� OSPF network command

–Requires entering:q g•network address•wildcard mask - the inverse of the subnet mask•area-id - area-id refers to the OSPF area OSPF area•area-id - area-id refers to the OSPF area. OSPF areais a group of routers that share link state information

Router(config-router)#network network-address wildcard-ask area area-idRouter(config router)#network network address wildcard ask area area id

255.255.255.255- 255.255.255.240 --------------------

0 0 0 15

Subtract the subnet mask

Wildcard mask0. 0. 0. 15

255.255.255.255- 255.255.255.252

Subtract the subnet mask

15© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

--------------------0. 0. 0. 03 Wildcard mask

Page 261: Nota CCNA Exp 2 - Routing Protocols and Concepts

Basic OSPF ConfigurationBasic OSPF Configuration� Cisco IOS now properly handles overlapping network ... area configuration commands.

� Consider the following example:g pfw#conf tEnter configuration commands, one per line. End with CNTL/Z.fw(config)#router ospf 100fw(config router)#network 0 0 0 0 255 255 255 255 area 0fw(config-router)#network 0.0.0.0 255.255.255.255 area 0fw(config-router)#network 10.0.0.0 0.0.3.255 area 113:06:57: %OSPF-6-AREACHG: 10.0.0.0 255.255.252.0 changed from area 0 to area 1fw(config-router)#network 10.0.0.0 0.0.0.7 area 213:07:10: %OSPF-6-AREACHG: 10.0.0.0 255.255.255.248 changed from area 1 to area 2fw(config-router)#^Z

� I've entered overlapping network statements, each one with a smaller address range. Not l d IOS d t t th t th l it l i t i l d donly does IOS detect that they overlap, it also prints nice syslog messages and reorders

the commands in the running configuration. Well done !fw#show run | begin router ospfrouter ospf 100plog-adjacency-changesnetwork 10.0.0.0 0.0.0.7 area 2network 10.0.0.0 0.0.3.255 area 1network 0 0 0 0 255 255 255 255 area 0

http://blog.ioshints.info/2006/11/network-statements-in-ospf-

ht l

16© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

network 0.0.0.0 255.255.255.255 area 0 process-are.html

Basic OSPF ConfigurationBasic OSPF Configuration� ospf network definition for adding all interfaces / default route

What’s the difference?router ospf 1network 0.0.0.0 0.0.0.0 area 0

vsvs.router ospf 1network 0.0.0.0 255.255.255.255 area 0

� Both add all existing interfaces into area 0 and all later added interfaces also. Both statements are valid.

http://blog.sazza.de/?p=427

17© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 262: Nota CCNA Exp 2 - Routing Protocols and Concepts

B i OSPF C fi tiBasic OSPF Configuration

� Area area id� Area area-id�An OSPF area is a group of routers that share link-state information.� In this chapter, we will configure all of the OSPF routers within a single area. This is known as single-area OSPF. �Multi-area OSPF is covered in CCNP.

18© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

B i OSPF C fi tiBasic OSPF Configuration� Router ID

– This is an IP address used to identify a router– 3 criteria for deriving the router ID

1 U IP dd fi d ith OSPF t id d1. Use IP address configured with OSPF router-id command-Takes precedence over loopback and physical interface

addresses2. If router-id command not used then router chooses highest

IP address of any loopback interfaces3 If no loopback interfaces are configured then the highest IP3. If no loopback interfaces are configured then the highest IP

address on any active physical interface is used� The interface does not need to be enabled for OSPF,

meaning that it does not need to be included in one of themeaning that it does not need to be included in one of theOSPF network commands.

� However, the interface must be active - it must be in the up state

19© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

up state.

However!!!!!!

Page 263: Nota CCNA Exp 2 - Routing Protocols and Concepts

B i OSPF C fi tiBasic OSPF Configuration

R t ID� Router IDIf th ki h th– If you are the king when thekingdom is built, you are thekingdom is built, you are theKING for life

– It means when ID is elected, it i th ID f th t lis the ID for the router, unless…………..

20© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Basic OSPF ConfigurationBasic OSPF ConfigurationOSPF Router ID� Commands used to verify current router ID

–Show ip protocols–Show ip ospf–Show ip ospf interface

21© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 264: Nota CCNA Exp 2 - Routing Protocols and Concepts

Basic OSPF ConfigurationBasic OSPF ConfigurationOSPF Router ID� Router ID (not configured) & Loopback addresses

(configured)–Highest loopback address will be used as router IDHighest loopback address will be used as router ID–Advantage of using loopback address the loopback interface cannot fail � OSPF stability

� The OSPF router-id commandThe OSPF router id command–Introduced in IOS 12.0–OSPF router-id command, which is a fairly recent addition to IOS, it is more common to find loopback, paddresses used for configuring OSPF router IDs.–Command syntax

�Router(config)#router ospf process-id�Router(config-router)#router-id ip-address

� Modifying the Router ID–Use the command Router#clear ip ospf process

22© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Use the command Router#clear ip ospf process

This command does not work in PT.

Basic OSPF ConfigurationBasic OSPF ConfigurationModifying the Router IDy g� The router ID is selected when OSPF is

configured with its first OSPF network command. – If the OSPF router-id command or the loopbackIf the OSPF router id command or the loopback

address is configured after the OSPF network command, the router ID will be derived from the interface with the highest active IP address.

f� Modifying the Router IDThe router ID can be modified with 1. the IP address from a subsequent OSPF router-id

command b reloading the ro ter orcommand by reloading the router or2. by using the following command:

Router#clear ip ospf process

3. Modifying a router ID with a new loopback or physical interface IP address may require reloading the router

23© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

reloading the router

Page 265: Nota CCNA Exp 2 - Routing Protocols and Concepts

Basic OSPF ConfigurationBasic OSPF ConfigurationDuplicate Router IDsDuplicate Router IDs� When two routers have the same router ID in

an OSPF domain, routing may not function properly.properly.

– If the router ID is the same on two neighboring routers, the neighbor establishment may not occur.

� When duplicate OSPF router IDs occur, IOS will display a message similar to:

– %OSPF-4-DUP_RTRID1: Detected router ith d li t t IDwith duplicate router ID

� To correct this problem, configure all routers so that they have unique OSPF router IDs.

� Because some IOS versions do not support the router-id command, we will use the loopback address method for assigning router IDs

24© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

router IDs.

Quick ReviewQuick Review

We just went over 3 different types of IDWe just went over 3 different types of ID� ospf process-id.

OSPF process– OSPF process.– Cannot be 0

� Area ID:� Area ID:– OFPS area– If it is the first, and the backbone area, it is 0, ,

� Router ID– Router ID– 1 IP address is elected per router,

• Highest physical address (or)

25© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

• Highest logical address (loopback)

Page 266: Nota CCNA Exp 2 - Routing Protocols and Concepts

Basic OSPF ConfigurationBasic OSPF ConfigurationVerifying OSPF

U th h i f d t if &� Use the show ip ospf command to verify &trouble shoot OSPF networks:

� Neighbor adjacency�Adjacency indicated by

�The OSPF state of the interface is “full state”full state

�No adjacency indicated by -�Neighboring router’s Router ID is not displayed�A state of full is not displayed

-Consequence of no adjacency-•Neighbor ID - The router ID of the neighboring router.•Pri - The OSPF priority of the interface..St t Th OSPF t t f th i t f FULL t tConsequence of no adjacency

�No link state information exchanged�Inaccurate SPF trees & routing tables

•State - The OSPF state of the interface. FULL statemeans that the router and its neighbor have identical OSPF link-state databases.•Dead Time - The amount of time remaining that the router will wait to receive an OSPF Hello packet from the neighbor before declaring the neighbor down. This value is reset when the interface receives a Hello packet

26© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

is reset when the interface receives a Hello packet.•Address - The IP address of the neighbor's interface to which this router is directly connected.•Interface - The interface on which this router has formed adjacency with the neighbor.

Basic OSPF ConfigurationBasic OSPF ConfigurationNote:� On multiaccess networks such as Ethernet,

two routers that are adjacent may have their states displayed as 2WAYstates displayed as 2WAY.

–This will be discussed in a DR and BDR section.

� Two routers may not form an OSPF dj ifadjacency if:

–The subnet masks do not match, causing the routers to be on separate networks. •Neighbor ID - The router ID of the neighboring router.

•Pri - The OSPF priority of the interface..St t Th OSPF t t f th i t f FULL t t

–OSPF Hello or Dead Timers do not match.–OSPF Network Types do not match.

Th i i i i t OSPF

•State - The OSPF state of the interface. FULL statemeans that the router and its neighbor have identical OSPF link-state databases.•Dead Time - The amount of time remaining that the router will wait to receive an OSPF Hello packet from the neighbor before declaring the neighbor down. This value is reset when the interface receives a Hello packet

27© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

–There is a missing or incorrect OSPFnetwork command.

is reset when the interface receives a Hello packet.•Address - The IP address of the neighbor's interface to which this router is directly connected.•Interface - The interface on which this router has formed adjacency with the neighbor.

Page 267: Nota CCNA Exp 2 - Routing Protocols and Concepts

Verifying OSPFVerifying OSPF� Show ip protocols

–OSPF process ID,p ,–the router ID, –networks the router is advertising, –the default administrative distance, 110 for OSPF.

� Show ip ospf–OSPF process ID –router IDrouter ID.–OSPF area information –the last time the SPF algorithm was calculated.

•R1 has participated in during the past 11 and a half hours is to send small Hello packets to its neighbors.

–SPF schedule delay •The router waits 5000 msecs after receiving an LSU before running the SPF algorithm. •There is an additional Hold Time of 10000 msecs between 2 SPF calculations.

� Show ip ospf interface

28© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

–The quickest way to verify Hello and Dead intervals• for OSPF routers to become neighbors, their OSPF Hello and Dead intervals must be identical.

Configuring OSPF loopback address and router priorityConfiguring OSPF loopback address and router priorityThe command show ip ospf interface will display the interface priority value as well as other key information.p y y

29© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 268: Nota CCNA Exp 2 - Routing Protocols and Concepts

Basic OSPF ConfigurationBasic OSPF ConfigurationExamining the routing table� Use the show ip route command to display the routing table

-An “O’ at the beginning of a route indicates that the router source is OSPFOSPF-OSPF does not automatically summarize at major network boundaries

•Loopbackinterface countsinterface countsas a network. •These loopback interfaces are not advertised in OSPF.•They function as

t ID

30© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

router ID.

OSPF M t iOSPF Metric� OSPF uses cost as the metric for determining the

best routebest route–A cost is associated with the output side of each router interface.

Th l th t th lik l th i t f i–The lower the cost, the more likely the interface isto be used to forward data traffic

� The Cisco IOS uses the cumulative b d idth f th t i i t f fbandwidths of the outgoing interfaces fromthe router to the destination network as the cost value.

C i b d b d id h f i f-Cost is based on bandwidth of an interface�Cost is calculated using the formula

108 / bandwidth-Reference bandwidth

�The 100Mbps (FastEthernet) and higher will have the same OSPF cost of 1.

31© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

�This reference bandwidth can be modified using�auto-cost reference-bandwidth command

Page 269: Nota CCNA Exp 2 - Routing Protocols and Concepts

OSPF MetricOSPF Metric� COST of an OSPF route is the accumulated value from

one router to the destination networkone router to the destination network•For example, in the figure, the routing table on R1 shows 64 + 1 65the routing table on R1 showsa cost of 65 to reach the 10.10.10.0/24 network on R2.

•Because 10.10.10.0/24

64 + 1 = 65

is attached to a FastEthernet interface, R2 assigns the value 1 asthe cost for 10.10.10.0/24. •R1 then adds the additional cost value of 64

d d hto send data across thedefault T1 link between R1 and R2.

32© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

OSPF MetricOSPF Metric� Sometimes the actual speed of a link is different than

the default bandwidthThi k it i ti th t th b d idth l fl t–This makes it imperative that the bandwidth value reflects

link’s actual speed�Reason: so routing table has best path information

� The show interface command will display interface’s� The show interface command will display interface sbandwidth

–Most serial link default to 1.544Mbps–However, some serial interfaces may default to 128 kbps.However, some serial interfaces may default to 128 kbps.

33© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 270: Nota CCNA Exp 2 - Routing Protocols and Concepts

M dif i OSPF t t iModifying OSPF cost metric� OSPF uses cost as the metric for determining the

best route. Cost is calculated using the formula 108/bandwidth,where bandwidth is expressed in bps. (Cost = 100,000,000/Bandwidth)

� The Cisco IOS automatically determines cost basedThe Cisco IOS automatically determines cost basedon the bandwidth of the interface.

� It is essential for proper OSPF operation that the correct interface bandwidth is set.

Router(config)#interface serial 0/0Router(config-if)#bandwidth 64

The default bandwidth for Cisco serial interfaces is 1 544 Mbps or 1544 kbps1.544 Mbps, or 1544 kbps.

2A/S 2TCOD has these 2 types of serial cards in the lab

34© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

OSPF Metric: BandwidthOSPF Metric: Bandwidth� Remember, this bandwidth value

does not actually affect the speed of the link; it is used by some routingthe link; it is used by some routingprotocols to compute the routing metric.

–It is important that the bandwidth l fl t th t l d f thvalue reflect the actual speed of the

link so that the routing table has accurate best path information.

� The figure displays the routing table g p y gfor R1.

–R1 believes that both of its serial interfaces are connected to T1 links,

f th li k i 64 kb li k•one of the links is a 64 kbps link•the other one is a 256 kbps link.

–This results in R1's routing table having two equal-cost paths to thehaving two equal cost paths to the192.168.8.0/30 network, when Serial 0/0/1 is actually the better path.

35© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

How to modify the cost of all the links?

Page 271: Nota CCNA Exp 2 - Routing Protocols and Concepts

Basic OSPF ConfigurationBasic OSPF ConfigurationModifying the Cost of a link

B th id f i l li k h ld b� Both sides of a serial link should beconfigured with the same bandwidth

–Commands used to modify bandwidth valueCommands used to modify bandwidth value�Bandwidth command

–Example: Router(config-if)#bandwidthbandwidth-kbps�ip ospf cost command – allows you to directly specify interface cost

-Example:R1(config)#interface serial 0/0/0R1(config-if)#ip ospf cost 1562

36© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

M dif i th C t f th li kModifying the Cost of the link� Difference between bandwidth command & the ip ospf

t dcost command–Ip ospf cost command

�Sets cost to a specific value�Sets cost to a specific value–Bandwidth command

�Link cost is calculated

37© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 272: Nota CCNA Exp 2 - Routing Protocols and Concepts

OSPF d M lti N t kOSPF and Multiaccess NetworksChallenges in Multiaccess Networks� OSPF defines five network types:� OSPF defines five network types:

–Point-to-point•network there are only two devices on the network, one at each end. ,

–Broadcast Multiaccess•a network with more than two devices on the same shared media. •all devices on the network see all broadcast frames.

–Nonbroadcast Multiaccess (NBMA)•networks include Frame Relay ATM•networks include Frame Relay, ATM,and X.25 networks.

–Point-to-multipoint•networks include Frame Relay, ATM,

d X 25 t kand X.25 networks.–Virtual links

•Virtual links are a special type of link that can be used in multi-area OSPF

38© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

can be used in multi area OSPF.

OSPF in Multiaccess Networks� 2 challenges presented by

multiaccess networks–Multiple adjacencies–Extensive LSA floodingExtensive LSA flooding

� The creation of an adjacency between every pair of routers in a network would create an unnecessary numberwould create an unnecessary numberof adjacencies.

–This would lead to an excessive number of LSAs passing betweennumber of LSAs passing betweenrouters on the same network.

•5 routers in the figure will need 10 adjacencies,j ,•10 routers would require 45 adjacencies.•20 routers would require 190

39© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

20 routers would require 190adjacencies

Page 273: Nota CCNA Exp 2 - Routing Protocols and Concepts

OSPF i M lti N t kOSPF in Multiaccess Networks� Extensive flooding of LSAsg

For every LSA sent out there must be an acknowledgement of receipt sent back to transmitting router.

consequence: lots of bandwidth consumed and chaotic traffic

40© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Solution:

Steps in the operation of OSPF � OSPF routers send Hello packets on OSPF enabled interfaces. � On multi-access networks the routers elect a DR and BDR On these networks other routersOn multi access networks, the routers elect a DR and BDR. On these networks other routers

become adjacent to the DR.

To reduce the number of adjacencies trafficsTo reduce the number of adjacencies each router must form, OSPF calls one of the routers the designated router. A designated router is elected as

f i dj i d h ll h bli hrouters are forming adjacencies, and then all other routers establishadjacencies only with the designated router. This simplifies the routing table update procedure and reduces the number of link-state records in the database. The designated router plays other important roles as well to reduce the overhead of a OSPF link-state procedures. For example, other routers send link-state advertisements it to the designated router only byg y yusing the all-designated-routers multicast address of 224.0.0.6.

41© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

http://www.chebucto.ns.ca/Chebucto/Technical/Manuals/Max/max6000/isptele/maxospf.htm

Page 274: Nota CCNA Exp 2 - Routing Protocols and Concepts

Steps in the operation of OSPF

� OSPF routers send Hello� OSPF routers send Hellopackets on OSPF enabled interfaces.

� On multi-access networks, the routers elect a DR and BDR. On these networks other routers become adjacent to the DR.

42© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Steps in the operation of OSPFSteps in the operation of OSPF� To reduce the number of adjacencies traffics

43© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

http://www.cisco.com/warp/public/104/11.html

Page 275: Nota CCNA Exp 2 - Routing Protocols and Concepts

OSPF i M lti N t kOSPF in Multiaccess Networks� Solution to LSA flooding issue is the use of

–Designated router (DR)–Backup designated router (BDR)

•this solution is analogous to electing i th t d d lsomeone in the room to go around and learn

everyone's names and then announce these names to everyone in the room at once.

–DROther• All other routers become DROthers (this indicates a router that is neither the DR or the BDR).DROth l f f ll dj i ith th•DROthers only form full adjacencies with the

DR and BDR in the network.

� DR & BDRO lti t k OSPF l t–On multiaccess networks, OSPF elects a

Designated Router (DR) to be the collection and distribution point for LSAs sent and received. –A Backup Designated Router (BDR) is also

44© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

p g ( )elected in case the Designated Router fails. –DR & BDR are elected to send & receive LSA

OSPF i M lti N t kOSPF in Multiaccess Networks� DR & BDR & DROther

–Routers on a multiaccess network elect a DR and BDR.

DR & BDR are elected to send &–DR & BDR are elected to send &receive LSA–DROthers only form full adjacencies with the DR and BDR inadjacencies with the DR and BDR inthe network.

� Sending & Receiving LSASending & Receiving LSA–DRothers send LSAs via multicast 224.0.0.6 to DR & BDR (ALLDRouters - All DR routers)(ALLDRouters All DR routers)–DR forward LSA via multicast address 224.0.0.5 to all other routers (AllSPFRouters - All OSPF routers)

45© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

(AllSPFRouters - All OSPF routers).

Page 276: Nota CCNA Exp 2 - Routing Protocols and Concepts

OSPF in Multiaccess Networks

DR/BDR Election ProcessDR/BDR Election Process

� DR/BDR elections DONOT occur in point to

� DR/BDR elections will take place on multiaccessNOT occur in point-to-

point networksplace on multiaccessnetworks as shown below

46© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

OSPF in Multiaccess NetworksOSPF in Multiaccess Networks

� Criteria for getting elected DR/BDRg g1. DR: Router with the highest OSPF

interface priority.2 BDR: Router with the second highest2. BDR: Router with the second highest

OSPF interface priority.3. If OSPF interface priorities are equal, the

highest router ID is used to break the tie.

47© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 277: Nota CCNA Exp 2 - Routing Protocols and Concepts

� Criteria for getting elected DR/BDR1. DR: Router with the highest OSPF interface

priority.p y2. BDR: Router with the second highest OSPF

interface priority.3. If OSPF interface priorities are equal, the

highest router ID is used to break the tie.� Example:

– The OSPF for all interface priority is 1The OSPF for all interface priority is 1.– The OSPF router ID is used to elect the DR

and BDR. • RouterC with the highest router ID,g ,

becomes the DR• RouterB, with the second highest router

ID, becomes the BDR. B R t A i t l t d• Because RouterA is not elected as either the DR or BDR, it becomes the DROther.

48© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

DROthers only form FULL adjacencies with the DR and BDR, but will still form a neighbor adjacency with any DROthers that join the network. When two DROther routers form a neighbor adjacency, the neighbor state is displayed as 2WAY.

You need 4 routers topology to see this “2way” adjacency.

OSPF network types (cont.)

Real DR and BDR election processThe first router up on the network is the DRDR.The second router up on the network is the BDR.If the DR fails then the BDR becomes DRIf the DR fails then the BDR becomes DRand another router is elected the BDR. The DR does not change just because another router comes on line with a highergpriority or a higher router id. If both the existing DR and BDR fail and a new DR must be elected, the router with the highest priority is elected DRthe highest priority is elected DR.If there's a tie, the router with the highest router id is elected DR.

49© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 278: Nota CCNA Exp 2 - Routing Protocols and Concepts

Timing of DR/BDR Election(This is really of how the election works)

� Election occurs as soon as 1st router has its OSPFElection occurs as soon as 1 router has its OSPFenabled on multiaccess network. This can happen when

1 When the routers are powered on1. When the routers are powered-on• it is possible that a router with a lower router ID will become the DR. This could be a lower-end router that took less time to bootrouter that took less time to boot.

2. when the OSPF network command for that interface is configured.

� When a DR is elected it remains as the DR until one of the following occurs

The DR fails-The DR fails.-The OSPF process on the DR fails.-The multiaccess interface on the DR fails.

50© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Timing of DR/BDR Election(This is really of how the election works)

� DR FailsDR Fails–If the DR fails, the BDR assumes the role of DR and an election is held to choose a new BDRBDR.–In the figure, RouterC fails and the former BDR, RouterB, becomes DR. The only otherBDR, RouterB, becomes DR. The only otherrouter available to be BDR is RouterA.

51© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 279: Nota CCNA Exp 2 - Routing Protocols and Concepts

Timing of DR/BDR Election(This is really of how the election works)

� New RouterNew Router–If a new router enters the network after the DR and BDR have been elected, it will

t b th DR th BDR if itnot become the DR or the BDR even if ithas a higher OSPF interface priority or router ID than the current DR or BDR.

•If the current DR fails, the BDR will become the DR, and the new router can be elected the new BDR.can be elected the new BDR.•After the new router becomes the BDR, if the DR fails, then the new

t ill b th DRrouter will become the DR.•The current DR and BDR must both fail before the new router can be

52© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

elected DR or BDR.

Timing of DR/BDR Election(This is really of how the election works)

� Old DR ReturnsOld DR Returns–A previous DR does not regain DR status if it returns to the network.

•In the figure, RouterC has finished a reboot and becomes a DROther even though its router ID, 192.168.31.33, isthough its router ID, 192.168.31.33, ishigher than the current DR and BDR.

53© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 280: Nota CCNA Exp 2 - Routing Protocols and Concepts

Timing of DR/BDR Election(This is really of how the election works)

� BDR FailsBDR Fails–If the BDR fails, an election is held among the DRothers to see which router

ill b th BDRwill be the new BDR.•In the figure, the BDR router fails. •An election is held between RouterC•An election is held between RouterCand RouterD. •RouterD wins the election with the higher router ID.

54© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Timing of DR/BDR Election(This is really of how the election works)

� New DR FailsNew DR Fails–In the figure, RouterB fails. Because RouterD is the current BDR, it is promoted to DR RouterC becomes the BDRto DR. RouterC becomes the BDR.

� So, how do you make sure that the routers you want to be DR and BDR ywin the election? Without further configurations, the solution is to either:either:

–Boot up the DR first, followed by the BDR, and then boot all other routers, or–Shut down the interface on all routers, followed by a no shutdown on the DR, then the BDR, and then all other routers.

55© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

OR: use the priority command set not desired DR and BDR to 0

Page 281: Nota CCNA Exp 2 - Routing Protocols and Concepts

OSPF in Multiaccess NetworksOSPF in Multiaccess NetworksOSPF Interface Priority� Manipulating the DR/BDR election process continued� Manipulating the DR/BDR election process continued

–Use the ip ospf priority interface command.–Example:Router(config-if)#ip ospf priority {0 - 255}

�Priority number range 0 to 255–0 means the router cannot become the DR or BDR–1 is the default priority value–1 is the default priority value

»router ID determined the DR and BDR

56© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

OSPF in Multiaccess NetworksOSPF in Multiaccess NetworksOSPF Interface Priority� Modify Priority� Modify Priority

–Router(config-if)#ip ospf priority {0 - 255}

� Force ElectionAft d i h td d h td–After doing a shutdown and a no shutdown

on the FastEthernet 0/0 interfaces of all three routers, we see the result of the change of OSPF interface priorities. –The show ip ospf neighbor command on RouterC now shows that RouterA (Router ID 192.168.31.11) is the DR with the highest OSPF interface priority of 200 DRp y–RouterB (Router ID 192.168.31.22) is still the BDR with the next highest OSPF interface priority of 100.

N ti f R t A' t t f h i BDR–Notice from RouterA's output of show ipospf neighbor that it does not show a DR, because RouterA is the actual DR on this network.

BDR

57© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 282: Nota CCNA Exp 2 - Routing Protocols and Concepts

More OSPF ConfigurationRedistrib ting an OSPF Defa lt Ro teRedistributing an OSPF Default Route� Topology includes a link to ISP

R t t d t ISP–Router connected to ISP�Called an autonomous system border router�Used to propagate a default route

In this topology, the Loopback1 (Lo1) simulate the connection to another Used to propagate a default route

–Example of static default routeR1(config)#ip route 0.0.0.0 0.0.0.0 loopback 1

router.

–Requires the use of the default-information originatecommandcommand–Example of default-information originate command

R1(config-router)#default-information originate

58© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Redistributing an OSPF Default Route

The default route in R2 and R3 with the routing source OSPF, but with the additional code, E2. For R2, the route is:

O*E2 0.0.0.0/0 [110/1] via 192.168.10.10, 00:05:34, Serial0/0/1

E2 denotes that this route is an OSPF ExternalE2 denotes that this route is an OSPF ExternalType 2 route. the cost of an E2 route is always the external cost, irrespective of the interior cost to reach that route. (CCNP)

59© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 283: Nota CCNA Exp 2 - Routing Protocols and Concepts

More OSPF ConfigurationMore OSPF ConfigurationFine-Tuning OSPF

� Since link speeds are getting faster it may be necessary to

fchange reference bandwidth values

Do this using the auto cost–Do this using the auto-costreference-bandwidth command–Example:� R1(config-router)#auto-costreference-bandwidth 10000

•the default value is equivalent to 100. To increase it to 10GigE speeds, you would need

60© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

g p , yto change the reference bandwidth to 10000.•Again, make sure you configure this command on all routers in the OSPF routing domain.

More OSPF ConfigurationMore OSPF ConfigurationFine-Tuning OSPF

� R1(config-router)#auto-cost reference-bandwidth 1000010000

•the default value is equivalent to 100. To increase it to 10GigE speeds you would needincrease it to 10GigE speeds, you would needto change the reference bandwidth to 10000.

R1 Before, the cost to 10.10.10.0/24 is 1172. Aft fi i f b d idth

61© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

After configuring a new reference bandwidth,the cost for the same route is now 117287.

Page 284: Nota CCNA Exp 2 - Routing Protocols and Concepts

More OSPF ConfigurationMore OSPF Configuration

Fine-Tuning OSPF� Modifying OSPF timers

–Reason to modify timers�Faster detection of network failures

–Manually modifying Hello & Dead intervals�Router(config-if)#ip ospf hello-interval secondsR t ( fi if)#i f d d i t l d�Router(config-if)#ip ospf dead-interval seconds

–Point to be made�Hello & Dead intervals must be the same between�Hello & Dead intervals must be the same betweenneighbors

62© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

The End

� Questions?� Questions?

What will be the result of the DR and BDR elections for this single areaWhat will be the result of the DR and BDR elections for this single areaOSPF network? (Choose three.)

HQ ill b DR f 10 4 0 0/16

*. Decision process:

1. Which segment will have election?HQ will be DR for 10.4.0.0/16.

Router A will be DR for 10.4.0.0/16.

HQ will be BDR for 10 4 0 0/16

2. Priority?

3. Router ID (each router will only has 1 ID)?HQ will be BDR for 10.4.0.0/16.

Router A will be DR for 10.5.0.0/16.

Remote will be DR for 10 5 0 0/16

ID)?

1. Set using “router-ID” command

2. Highest Loopback IP address?

63© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Remote will be DR for 10.5.0.0/16.

Remote will be BDR for 10.5.0.0/16.3. Highest physical IP address

(include serial interface)?

Page 285: Nota CCNA Exp 2 - Routing Protocols and Concepts

The End

� Questions?� Questions?

The routers in the diagram are configured as shown The loopback interface onThe routers in the diagram are configured as shown. The loopback interface onrouter R1 is labeled as lo0. All OSPF priorities are set to the default except for Ethernet0 of router R2, which has an OSPF priority of 2. What will be the result of the OSPF DR/BDR elections on the 192.1.1.0 network? (Choose two.)the OSPF DR/BDR elections on the 192.1.1.0 network? (Choose two.)

R1 will be the DR *. Decision process:

1 Which segment will have election?R1 will be the BDR

R2 will be the DR

1. Which segment will have election?

2. Priority?

3. Router ID (each router will only has 1 ID)?R2 will be the BDR

R3 will be the DR1. Set using “router-ID” command

2. Highest Loopback IP address?

64© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

R3 will be the BDR 3. Highest physical IP address (include serial interface)?

� Questions?� Questions?

*. Decision process:

1 Which segment will have election?1. Which segment will have election?

2. Priority?

3. Router ID (each router will only has 1 ID)?

1. Set using “router-ID” command

2. Highest Loopback IP address?

65© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

3. Highest physical IP address (include serial interface)?

Page 286: Nota CCNA Exp 2 - Routing Protocols and Concepts

� Questions?

Answer?????Answer?????

*. Decision process:

1. Which segment will have election?

2 i i ?2. Priority?

3. Router ID (each router will only has 1 ID)?

1. Set using “router-ID” command1. Set using router ID command

2. Highest Loopback IP address?

3. Highest physical IP address (include i l i f )?

66© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

serial interface)?

� Questions?

Answer?????� HQ will be DR for

10.4.0.0/16

Answer?????

� Router A will be DR for 10.4.0.0/16.

HQ ill b BDR f� HQ will be BDR for10.4.0.0/16.

� Router A will be DR for*. Decision process:

1 Which segment will have election?Router A will be DR for10.5.0.0/16

� Remote will be DR for

1. Which segment will have election?

2. Priority?

3. Router ID (each router will only has 1 ID)?10.5.0.0/16.

� Remote will be BDR for 10 5 0 0/16

1. Set using “router-ID” command

2. Highest Loopback IP address?

67© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

10.5.0.0/16 3. Highest physical IP address (include serial interface)?

Page 287: Nota CCNA Exp 2 - Routing Protocols and Concepts

SummarySummary� RFC 2328 describes OSPF link state concepts and

operationsoperations

� OSPF Characteristics–A commonly deployed link state routing protocol–Employs DRs & BDRs on multi-access networks

�DRs & BDRs are elected�DRs & BDRs are elected�DR & BDRs are used to transmit and receive LSAs

–Uses 5 packet types:Uses 5 packet types:1: HELLO2: DATABASE DESCRIPTION3: LINK STATE REQUEST4: LINK STATE UPDATE5: LINK STATE ACKNOWLEDGEMENT

68© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

5: LINK STATE ACKNOWLEDGEMENT

Summary

� OSPF Characteristics� OSPF Characteristics–Metric = cost

�Lowest cost = best path�Lowest cost = best path

� ConfigurationE bl OSPF t i th f ll i d–Enable OSPF on a router using the following command�R1(config)#router ospf process-id

use the network command to define which interfaces will–use the network command to define which interfaces willparticipate in a given OSPF process

�R1(config-router)#network network-addresswildcard-mask area area-id

69© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara

Page 288: Nota CCNA Exp 2 - Routing Protocols and Concepts

Summary

� Verifying OSPF configuration–Use the following commands

�show ip protocol�show ip route

h i f i t f�show ip ospf interface�show ip ospf neighbor

70© 2010 Cisco Systems, Inc. All rights reserved. Institut Tadbiran Awam Negara