Goals that we wants for our IGRP implementation · stable routing even in very large or complex networks. No routing loops should occur, even as transients. · fast response to changes in network topology · low overhead. That is, IGRP itself should not use more bandwidth than what is actually needed for its task. · splitting traffic among several parallel routes when they are of roughly equal desirability. · taking into account error rates and level of traffic on different paths · the ability to handle multiple "types of service" with a single set of information. Why we are using IGRP As mentioned above, IGRP is a protocol that allows gateways to build up their routing table by exchanging information with other gateways. A gateway starts out with entries for all of the networks that are directly connected to it. It gets information about other networks by exchanging routing updates with adjacent gateways. In the simplest case, the gateway will find one path that represents the best way to get to each network. A path is characterized by the next gateway to which packets should be sent, the network interface that should be used, and metric information. Metric information is a set of numbers that characterize how good the path is. This allows the gateway to compare paths that it has heard from various gateways and decide which one to use. There are often cases where it makes sense to split traffic between two or more paths. IGRP will do this whenever two or more paths are equally good. The user can also configure it to split traffic when paths are almost equally good. In this case more traffic will be sent along the path with the better metric. The intent is that traffic can be split between a 9600 bps line and a 19200 BPS line, and the 19200 line will get roughly twice as much traffic as the 9600 BPS line. How to implement IGRP on your network The steps to configure IGRP as the network's routing protocol are as follows: o Complete these commands from the router console position. Log into the router at user mode using the Cisco password. o Ping all interfaces on your router and the direct neighboring routers. Make sure that all connectivity is successful. o Use the command Show IP protocols. Nothing should display because there are no ip protocols currently running. o Enter enable exec mode using the password Class. o Display the current running-config to determine if any static routes have been defined (Show Running-Config). This would consist of RIP, etc. o Enter the configuration mode by entering the config term command (Config Term). The router prompt should change to Lab-x(config)# o Use the IGRP command to begin setting this protocol for the routers. Use the Router IGRP 100 command. The router prompt should change to Lab-x(config-router)#. o Enter the IP network address for each of the networks directly connected to the router. Example: At the Lab-x(config-router)# prompt, type Network xxx.xxx.xxx.xxx. If the prompt comes back with no response, the command has been accepted. o The above step needs to be repeated for all networks directly connected to the router. o Exit or use Control Z to return to enable mode--Lab-x# o Enter the command Show Running-Config. The IGRP protocol should be turned on (should look as follows) Router IGRP 100 network xxx.xxx.xxx.xxx o The next step should be to Copy Running Start to place this into the start-up configuration file from |
| Traffic Flow and Routing Update |