Cisco Systems 78-11741-02 Creating the Igrp Routing Process, Allowing Unicast Updates for Igrp

Configuring IGRP

IGRP Configuration Task List

•Disabling Holddown (Optional)

•Enforcing a Maximum Network Diameter (Optional)

•Validating Source IP Addresses (Optional)

•Enabling or Disabling Split Horizon (Optional)

Also see the examples in the “IGRP Configuration Examples” section at the end of this chapter.

Creating the IGRP Routing Process

To create the IGRP routing process, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1
	Router(config)# router igrp as-number	Enables an IGRP routing process, which places you
		in router configuration mode.
Step 2
	Router(config-router)# network network-number	Associates networks with an IGRP routing process.

IGRP sends updates to the interfaces in the specified networks. If the network of an interface is not specified, the interface will not be advertised in any IGRP update.

It is not necessary to have a registered autonomous system number to use IGRP. If you do not have a registered number, you are free to create your own. We recommend that if you do have a registered number, you use it to identify the IGRP process.

Applying Offsets to Routing Metrics

An offset list is the mechanism for increasing incoming and outgoing metrics to routes learned via IGRP. Applying an offset limit is done to provide a local mechanism for increasing the value of routing metrics. Optionally, you can limit the offset list with either an access list or an interface. To increase the value of routing metrics, use the following command in router configuration mode:

Command	Purpose
Router(config-router)# offset-list[access-list-number	Applies an offset to routing metrics.
access-list-name] {in out} offset [interface-type
interface-number]

Allowing Unicast Updates for IGRP

Because IGRP is normally a broadcast protocol, in order for IGRP routing updates to reach nonbroadcast networks, you must configure the Cisco IOS software to permit this exchange of routing information.

To permit information exchange, use the following command in router configuration mode:

Command	Purpose
Router(config-router)# neighbor ip-address	Defines a neighboring router with which to exchange
	routing information.
	Cisco IOS IP Configuration Guide

IPC-215