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Configuring IGRP
IGRP Configuration Task List
IPC-215
Cisco IOS IP Configuration Guide
• 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:
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:
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
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.
Command Purpose
Router(config-router)# offset-list [access-list-number |
access-list-name] {in | out} offset [interface-type |
interface-number]
Applies an offset to routing metrics.
Command Purpose
Router(config-router)# neighbor ip-address
Defines a neighboring router with which to exchange
routing information.