89 - 238 CCNA 2: Routers and Routing Basics v3.1 Instructor Guide – Module 7 Copyright © 2004, Cisco Systems, Inc.
The debug ip igrp events command can be used to verify that the timers affect routing
updates. Have the students configure IGRP on the lab topology.
7.3.5 Configuring IGRP
To enable IGRP routing use the router igrp as-number global configuration command.
To disable IGRP routing use the no router igrp as-number command.
RouterA(config)#router igrp as-number
RouterA(config-router)#
RouterA(config)#no router igrp as-number
RouterA(config)#
To identify which networks will participate in the IGRP routing process, use the network
network-address router configuration command. To remove a network from the IGRP
routing process, use the no network network-address command.
RouterA(config)#router igrp 101
RouterA(config-router)#network 192.168.1.0
RouterA(config)#router igrp 101
RouterA(config-router)#no network 192.168.1.0
The autonomous system number is used to identify the router to other IGRP routers and to tag
routing information. Have the students configure IGRP on the lab topology.
7.3.6 Migrating from RIP to IGRP
With the creation of the IGRP in the early 80s, Cisco Systems was the first company to solve
the problems associated with RIP. IGRP was designed to have a greater maximum hop count,
which gave it more scalability for larger companies. IGRP uses multiple metrics to determine
the best path, bandwidth, and delay, as opposed to the hop count metric used by RIP. As a
result of these improvements, IGRP enabled many large, complex, and topologically diverse
internetworks to be deployed. Have the students configure the lab topology with RIP and then
migrate to IGRP. Make sure that students understand that RIP is still the most implemented
routing protocol in smaller internetworks. Also, emphasize that IGRP can only be used in a
fully Cisco environment.
7.3.7 Verifying IGRP Configuration
The following commands and available switches can be used to verify the configuration of
IGRP:
• show interface
• show ip protocol
• show ip route
• show running-config
The show interface command can be used to verify issues that are specifically related to
the interface configuration such as the ip address, physical connectivity, and keepalives. The
show ip protocol command should be used to verify that routing protocols are correctly
configured. This command can be used to view the routing protocols enabled on the router,