Dynamic Routing

Chapter 9.

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CHAPTER OBJECTIVES

At the end of this Chapter you will be able to:

Explain Dynamic Routing Identify dynamic routing protocols Configure RIP,IGRP,OSPF and EIGRP protocols

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Dynamic RoutingWhat is Dynamic Routing?

Dynamic routing is when protocols (Routing Protocols) are used to find networks and update routing tables on routers.

This is easier than using static or default routing, but it’ll cost in terms of router CPU processes and bandwidth on the network links.Advantages of Dynamic Routing

The chief advantages of dynamic routing over static routing are scalability and adaptability.

A dynamically routed network can grow more quickly and larger, and is able to adapt to changes in the network topology brought about by this growth or by the failure of one or more network components.

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Disadvantages of Dynamic Routing

It increases complexity. Communicating information about network topology is not as simple as saying. Protocols Routed Protocol Routing Protocol

What are Routed Protocols?ROUTED PROTOCOLS are used to transmit data across the networks. Routed protocols include:Telnet Internet ProtocolRemote Procedure Call (RPC) SNMPSMTP Novell IPX Apple Talkpowered by DJ 4

Routing ProtocolsROUTING PROTOCOLS are the software that allow routers to dynamically advertise and learn routes, determine which routes are available and which are the most efficient routes to a destination.

Two types of routing protocols are used in internetworks:

1) Interior gateway protocols (IGPs): IGPs are used to exchange routing information with routers in the same autonomous system (AS). An autonomous system is one network or sets of networks under a single administrative control

Some IGP are:Routing Information Protocol(RIP) Interior gateway Routing Protocol (IGRP) Open Shortest path First (OSPF)Enhanced Interior gateway Routing Protocol (EIGRP)

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2) Exterior gateway protocols (EGPs): EGPs are used to communicate between ASes. An example of an EGP is Border Gateway Protocol (BGP), which is beyond the scope of this book

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Routing Protocol Basics

Administrative Distances:-The administrative distance (AD) is used to rate the trustworthiness of routing information received on a router from a neighbor router. An administrative distance is an integer from 0 to 255, where 0 is the most trusted and 255 means no traffic will be passed via this routeTable next page shows the default administrative distances that a Cisco router uses to decide which route to take to a remote network.

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Route Source  Default AD Connected interface 0Static route 1

Enhanced IGRP summary route 5

External BGP 20Internal Enhanced IGRP 90IGRP 100OSPF 110IS-IS 115RIP 120EGP 140External Enhanced IGRP 170Internal BGP 200Unknown 255

Default Administrative Distancespowered by DJ 8

Types of Dynamic Routing ProtocolsThere are three classes of routing protocols:1)Distance vector

The distance-vector protocols find the best path to a remote network by judging distance. Each time a packet goes through a router, that’s called a hop. The route with the least number of hops to the network is determined to be the best route. The vector indicates the direction to the remote network.

Both RIP and IGRP are distance-vector routing protocols. They send the entire routing table to directly connected neighbors.

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2)Link state:-

In link-state protocols, also called shortest-path-first protocols, the routers each create three separate tables. One of these tables keeps track of directly attached neighbors, one determines the topology of the entire internetwork, one is used as the routing table.

Link-state routers know more about the internetwork than any distance vector routing protocol.OSPF is an IP routing protocol that is completely link state. Link state protocols send updates containing the state of their own links to all other routers on the network.powered by DJ 10

3)Hybrid :-

Hybrid protocols use aspects of both distance vector and link state

For example: EIGRP.

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1) Distance Vector Protocol

RIP uses only hop count to determine the best path to a network.

If RIP finds more than one link with the same hop count to the

same remote network, it will automatically perform a round-robin

load balancing. RIP can perform load balancing for up to six

equal-cost links (four by default).

a) RIP supports only 15 hop count b) RIP version 1 uses only classful routing, which

means that all devices in the network must use the same subnet

mask c) RIP version 2 supports classless routing, which

means that all devices in the network can use different subnet

mask

Routing Information Protocol

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Configuration

Configuring RIP Routing

Let’s use a simple network example, shown in Figure below, to illustrate configuring RIPv1.

RIP Routing in Actionpowered by DJ 13

Conti..Here’s RouterA’s configuration:RouterA(config)# router ripRouterA(config-router)# network 192.168.1.0RouterA(config-router)# network 192.168.2.0

Here’s RouterB’s configuration:RouterB(config)# router ripRouterB(config-router)# network 192.168.2.0RouterB(config-router)# network 192.168.3.0

Troubleshooting IP RIPOnce you have configured IP RIP, you have a variety of commands available to view and troubleshoot your configuration and operation of RIP:

show ip protocolsshow ip routedebug ip rippowered by DJ 14

Interior gateway Routing Protocol (IGRP) a.Interior Gateway Routing Protocol (IGRP) is a Cisco-proprietary distance-vector routing protocol. This means that to use IGRP in your network, all your routers must be Cisco routers. Cisco created this routing protocol to overcome the problems associated with RIP.

b. IGRP has a maximum hop count of 255 with a default of 100. this is helpful in larger net- works and solves the problem of 15 hops being the maximum possible in a RIP network.

c. The main difference between RIP and IGRP configuration is that when you configure IGRP, you supply the autonomous system number. All routers must use the same number in order to share routing table information.

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Syntax of Configuration using IGRP

Setting up IGRP is almost as simple as configuring RIP:

Router(config)# router igrp autonomous_system_#

Router(config-router)# network IP_network_#

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Configuration Example

Let’s take the example shown in Figure below, to help illustrate how to configure IGRP on a router. Here’s the complete configuration of the router:

IP IGRP Configuration Examplepowered by DJ 18

CommandsRouter(config)# router igrp 100Router(config-router)# network 172.16.0.0Router(config-router)# network 192.168.1.0Router(config-router)# exitRouter(config)# interface ethernet 0Router(config-if)# ip address 172.16.1.1 255.255.255.0Router(config-if)# no shutdownRouter(config-if)# exitRouter(config)# interface ethernet 1Router(config-if)# ip address 172.16.2.1 255.255.255.0Router(config-if)# no shutdownRouter(config-if)# exitRouter(config)# interface ethernet 2Router(config-if)# ip address 192.168.1.65 255.255.255.192Router(config-if)# no shutdownRouter(config-if)# exitpowered by DJ 19

Conti..Router(config)# interface ethernet 3Router(config-if)# ip address 192.168.1.129 255.255.255.192Router(config-if)# no shutdownRouter(config-if)# exit

Troubleshooting IP IGRPYou have the same tools available to you in IGRP as you did in RIP to help troubleshoot the routing protocol:

show ip protocolsshow ip routedebug ip igrp eventsdebug ip igrp transactions

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Open Shortest path First (OSPF)

1) Link State Protocol

OSPF is a link-state Dynamic Routing protocol, OSPF provides the following features:

1) consists of areas and autonomous systems2) Minimizes routing update traffic3) Allows scalability4) Supports VLSM/CIDR5) Has unlimited hop count6) Allows multi-vendor deployment (open standard)

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Conti…

Typical OSPF Simple Design

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CommandsLet’s look at some code examples to see how the wildcard mask works. Router(config)# router ospf 1Router(config-router)# network 10.1.1.1 0.0.0.0 area 0Router(config-router)# network 10.1.2.1 0.0.0.0 area 0Router(config-router)# network 172.16.1.1 0.0.0.0 area 0Router(config-router)# network 172.16.2.1 0.0.0.0 area 0Troubleshooting OSPF

Once you have configured OSPF, you have a variety of commands available to view and troubleshoot your configuration and operation of OSPF:•show ip protocols•show ip route•show ip ospf interface•show ip ospf neighborpowered by DJ 23

3) Hybrid Protocol

Enhanced Interior gateway Routing Protocol (EIGRP) Like IGRP, EIGRP uses only bandwidth and delay of the line to determine the best path To a remote network. EIGRP routers that belong to different autonomous systems (ASes) don’t automatically share routing information and they don’t become neighbors.Features of EIGRP Routing:-a Support for IP, IPX, and AppleTalk via protocol-dependent modules.b. Considered classless (same as RIPv2 and OSPF)c. Support for VLSM/CIDRd. Support for summaries and discontiguous networkse. Efficient neighbor discoveryf. Communication via Reliable Transport Protocol (RTP).g. Support for multiple ASes on a single routerpowered by DJ 24

Configuration Example

Let’s look at an example, to illustrate how to configure EIGRP on a router. Here’s the routing configuration of the router: Router(config)# router eigrp 200Router(config-router)# network 172.16.0.0Router(config-router)# network 10.0.0.0

Troubleshooting EIGRPHere are some of the main commands used when viewing and troubleshooting EIGRP:•show ip protocols•show ip route•show ip eigrp neighbors•show ip eigrp topology•show ip eigrp traffic•debug ip eigrppowered by DJ 25

THANK YOU

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