Cisco Systems 78-11741-02 manual Restrictions to RIP Route Summarization, IPC-205

Configuring Routing Information Protocol

RIP Configuration Task List

Restrictions to RIP Route Summarization

Supernet advertisement (advertising any network prefix less than its classful major network) is not allowed in RIP route summarization, other than advertising a supernet learned in the routing tables. Supernets learned on any interface that is subject to configuration are still learned. For example, the following summarization is invalid:

interface E1

.

.

.

ip summary-address rip 10.0.0.0 252.0.0.0 (invalid supernet summarization)

Each route summarization on an interface must have a unique major net, even if the subnet mask is unique. For example, the following is not permitted:

interface Ethernet1

.

.

.

ip summary-address rip 10.1.0.0 255.255.0.0

ip summary-address rip 10.2.0.0 255.255.0.0 (or different mask)

Note The ip summary-address eigrp router configuration command uses other options that are not applicable to RIP. Do not confuse Enhanced IGRP (EIGRP) summary address with the new RIP command, ip summary-address rip.

Configuring Route Summarization on an Interface

The ip summary-address rip router configuration command causes the router to summarize a given set of routes learned via RIP Version 2 or redistributed into RIP Version 2. Host routes are especially applicable for summarization. To configure IP summary addressing, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1
	Router(config)# interface ethernet1	Enters interface configuration mode for the ethernet 1
		port.
Step 2
	Router(config-if)#ip summary-address rip ip_address	Specifies the IP address and network mask that
	ip_network_mask	identify the routes to be summarized.

See the “Route Summarization Examples” section at the end of this chapter for examples of using split horizon.

Verifying IP Route Summarization

You can verify which routes are summarized for an interface using the show ip protocols EXEC command. The following example shows potential summarizations and the associated interface summary address and network mask for Ethernet interface 2:

router# show ip protocols

Routing Protocol is "rip"

Sending updates every 30 seconds, next due in 8 seconds

Cisco IOS IP Configuration Guide

IPC-205