Configuring Split Horizon - Cisco Catalyst 3750 Software Configuration Manual

Metro switch

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Table of Contents

Configuring IP Unicast Routing

This example shows how to configure a router for IGRP and assign it autonomous system 109. The

network router configuration commands show the networks directly connected to the router.

Switch(config)# router igrp 109

Switch(config-router)# network 131.108.0.0

Switch(config-router)# network 192.31.7.0

Configuring Split Horizon

Routers connected to broadcast-type IP networks and using distance-vector routing protocols normally

use the split-horizon mechanism to reduce the possibility of routing loops. Split horizon blocks

information about routes from being advertised by a router on any interface from which that information

originated. This feature can optimize communication among multiple routers, especially when links are

In general, we do not recommend disabling split horizon unless you are certain that your application

requires it to properly advertise routes.

Beginning in privileged EXEC mode, follow these steps to disable split horizon on the interface:

configure terminal

interface interface-id

ip address ip-address subnet-mask

no ip split-horizon

show ip interface interface-id

copy running-config startup-config

To enable the split horizon mechanism, use the ip split-horizon interface configuration command.

Enter global configuration mode.

Enter interface configuration mode, and specify the interface to

Configure the IP address and IP subnet.

Disable split horizon on the interface.

Return to privileged EXEC mode.

Verify your entries.

(Optional) Save your entries in the configuration file.

Catalyst 3750 Metro Switch Software Configuration Guide

Configuring IGRP