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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 22 Configuring IP Unicast Routing
Configuring IGRP
This is an example of output from the show ip protocols privileged EXEC command that verifies the
IGRP configuration.
Switch# show ip protocols
<output truncated>
Routing Protocol is "igrp 109"
Sending updates every 90 seconds, next due in 52 seconds
Invalid after 270 seconds, hold down 280, flushed after 630
Outgoing update filter list for all interfaces is
Incoming update filter list for all interfaces is
Default networks flagged in outgoing updates
Default networks accepted from incoming updates
IGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0
IGRP maximum hopcount 100
IGRP maximum metric variance 1
Redistributing: igrp 109
Maximum path: 4
Routing for Networks:
131.108.0.0
183.31.0.0
Routing Information Sources:
Gateway Distance Last Update
Distance: (default is 100)
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
broken.
Note
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:
To enable the split horizon mechanism, use the ip split-horizon interface configuration command.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Enter interface configuration mode, and specify the interface to
configure.
Step 3
ip address ip-address subnet-mask
Configure the IP address and IP subnet.
Step 4
no ip split-horizon
Disable split horizon on the interface.
Step 5
end
Return to privileged EXEC mode.
Step 6
show ip interface interface-id
Verify your entries.
Step 7
copy running-config startup-config
(Optional) Save your entries in the configuration file.