Reference Guide

Summarize Routes
Routes in the RIPv2 routing table are summarized by default, thus reducing the size of the routing table
and improving routing efficiency in large networks.
By default, the autosummary command in ROUTER RIP mode is enabled and summarizes RIP routes up
to the classful network boundary.
If you must perform routing between discontiguous subnets, disable automatic summarization. With
automatic route summarization disabled, subnets are advertised.
The autosummary command requires no other configuration commands. To disable automatic route
summarization, enter no autosummary in ROUTER RIP mode.
NOTE: If you enable the ip split-horizon command on an interface, the system does not
advertise the summarized address.
Controlling Route Metrics
As a distance-vector protocol, RIP uses hop counts to determine the best route, but sometimes the
shortest hop count is a route over the lowest-speed link.
To manipulate RIP routes so that the routing protocol prefers a different route, manipulate the route by
using the offset command.
Exercise caution when applying an offset command to routers on a broadcast network, as the router
using the offset command is modifying RIP advertisements before sending out those advertisements.
The distance command also allows you to manipulate route metrics. To assign different weights to
routes so that the ones with the lower weight or administrative distance assigned are preferred, use the
distance command.
To set route matrixes, use the following commands.
• Apply a weight to all routes or a specific route and ACL.
ROUTER RIP mode
distance weight [ip-address mask [access-list-name]]
Configure the following parameters:
– weight: the range is from 1 to 255. The default is 120.
– ip-address mask: the IP address in dotted decimal format (A.B.C.D), and the mask in slash
format (/x).
– access-list-name: the name of a configured IP ACL.
• Apply an additional number to the incoming or outgoing route metrics.
ROUTER RIP mode
offset-list access-list-name {in | out} offset [interface]
Configure the following parameters:
– prefix-list-name: the name of an established Prefix list to determine which incoming routes
are modified
– offset: the range is from 0 to 16.
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Routing Information Protocol (RIP)