Dynamic Routing Chapter 9. powered by DJ 1

C HAPTER O BJECTIVES 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 powered by DJ 2

Dynamic Routing What 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. powered by DJ 3

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 Protocol  Remote Procedure Call (RPC)  SNMP  SMTP  Novell IPX  Apple Talk powered by DJ 4

Routing Protocols ROUTING 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) powered by DJ 5

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 powered by DJ 6

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 route Table next page shows the default administrative distances that a Cisco router uses to decide which route to take to a remote network. powered by DJ 7

Route Source Default AD Connected interface0 Static route1 Enhanced IGRP summary route5 External BGP20 Internal Enhanced IGRP90 IGRP100 OSPF110 IS-IS115 RIP120 EGP140 External Enhanced IGRP170 Internal BGP200 Unknown255 Default Administrative Distances powered by DJ 8

Types of Dynamic Routing Protocols There 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. powered by DJ 9

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. powered by DJ 11

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 powered by DJ 12

Configuration Configuring RIP Routing Let’s use a simple network example, shown in Figure below, to illustrate configuring RIPv1. RIP Routing in Action powered by DJ 13

Conti.. Here’s RouterA’s configuration: RouterA(config)# router rip RouterA(config-router)# network RouterA(config-router)# network Here’s RouterB’s configuration: RouterB(config)# router rip RouterB(config-router)# network RouterB(config-router)# network Troubleshooting IP RIP Once you have configured IP RIP, you have a variety of commands available to view and troubleshoot your configuration and operation of RIP:  show ip protocols  show ip route  debug ip rip powered 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. powered by DJ 15

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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_# powered by DJ 17

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 Example powered by DJ 18

Commands Router(config)# router igrp 100 Router(config-router)# network Router(config-router)# network Router(config-router)# exit Router(config)# interface ethernet 0 Router(config-if)# ip address Router(config-if)# no shutdown Router(config-if)# exit Router(config)# interface ethernet 1 Router(config-if)# ip address Router(config-if)# no shutdown Router(config-if)# exit Router(config)# interface ethernet 2 Router(config-if)# ip address Router(config-if)# no shutdown Router(config-if)# exit powered by DJ 19

Conti.. Router(config)# interface ethernet 3 Router(config-if)# ip address Router(config-if)# no shutdown Router(config-if)# exit Troubleshooting IP IGRP You have the same tools available to you in IGRP as you did in RIP to help troubleshoot the routing protocol:  show ip protocols  show ip route  debug ip igrp events  debug ip igrp transactions powered by DJ 20

 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 systems 2) Minimizes routing update traffic 3) Allows scalability 4) Supports VLSM/CIDR 5) Has unlimited hop count 6) Allows multi-vendor deployment (open standard) powered by DJ 21

Conti… Typical OSPF Simple Design powered by DJ 22

Commands Let’s look at some code examples to see how the wildcard mask works. Router(config)# router ospf 1 Router(config-router)# network area 0 Router(config-router)# network area 0 Router(config-router)# network area 0 Router(config-router)# network area 0 Troubleshooting 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 neighbor powered 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/CIDR d. Support for summaries and discontiguous networks e. Efficient neighbor discovery f. Communication via Reliable Transport Protocol (RTP). g. Support for multiple ASes on a single router powered 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 200 Router(config-router)# network Router(config-router)# network Troubleshooting EIGRP Here 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 eigrp powered by DJ 25

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