Configuring Split Horizon - Cisco WS-C3560-48PS-S Software Configuration Manual

Chapter 30 Configuring IP Unicast Routing
Command
Step 8 no metric holddown
Step 9
metric maximum-hops hops
Step 10
no validate-update-source
Step 11
variance multiplier
Step 12 traffic-share {balanced | min}
Step 13
end
Step 14 show ip protocols
Step 15 copy running-config startup-config
To shut down an IGRP routing process, use the no router igrp global configuration command.
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
broken.
78-16156-01
Purpose
(Optional) Disable the IGRP hold-down period. The route to a network is
placed in holddown if the router learns that the network is farther away than
previously known or is down. Holddown keeps new routing information
from being used for a certain period of time. This can prevent routing loops
caused by slow convergence. It is sometimes advantageous to disable
holddown to increase the network's ability to quickly respond to topology
changes; this command provides this function.
Use the metric holddown command if other routers or access servers
within the IGRP autonomous system are not configured with the no metric
holddown command. If all routers are not configured the same way, you
increase the possibility of routing loops.
(Optional) Configure the maximum network diameter. Routes with hop
counts exceeding this diameter are not advertised. The default is 100 hops;
the maximum is 255 hops.
(Optional) Disable validation of the source IP address of incoming RIP
routing updates. By default, the switch validates the source IP address of
incoming RIP routing updates and discards the update if the source address
is not valid.
(Optional) Define the variance associated with a particular path to enable
unequal-cost load balancing if desired, balancing traffic across all feasible
paths to converge to a new path if a path should fail. The multiplier can be
from 1 to 128; the default is 1 (equal-cost load balancing).
(Optional) Distribute traffic by one of these methods:
balanced—Proportionately to the ratios of metrics
•
min—By the minimum-cost route.
•
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
Catalyst 3560 Switch Software Configuration Guide
Configuring IGRP
30-27