summary-address (OSPF)

To create aggregate addresses for the Open Shortest Path First (OSPF) protocol, use the summary-address command. To return to the default, use the no form of this command.

summary-address ip-prefix/length [ not-advertise ] [ tag tag ]

no summary-address ip-prefix/length [ not-advertise ] [ tag tag ]

Syntax Description

ip-prefix/length
IP prefix designated for a range of addresses, including the prefix length. Specify ip-prefix as an IP address. Specify length as a number from 1 to 31.
not-advertise
(Optional) Suppresses routes that match the specified prefix/length pair.
tag tag
(Optional) Specifies the tag value that can be used as a match value for controlling redistribution using route maps. The range is from 1 to 65535.

Command Default

None

Command Modes

Router configuration mode

Command History

Release
Modification
5.0(3)N1(1)
This command was introduced.

Usage Guidelines

Use the summary-address command to create an aggregate address to replace a series of more-specific addresses. The metric used to advertise the summary is the smallest metric of all the more specific routes.

Use this command to help reduce the size of the routing table and allow an OSPF Autonomous System Boundary Router (ASBR) to advertise one external route as an aggregate for all redistributed routes that are covered by the address.

This command requires the LAN Base Services license.

Examples

This example shows how to configure the summary address 192.0.0.0 to include address 192.0.1.0, 192.0.2.0, 192.0.3.0, and so on. Only the address 192.0.0.0 is advertised in an external link-state advertisement.

switch(config)# router ospf 201
switch(config-router)# summary-address 192.0.0.0/16
switch(config-router)#

Related Commands

Command
Description
copy running-config startup-config
Saves the configuration changes to the startup configuration file.
redistribute (OSPF)
Redistributes external routing protocol routes into OSPF.
show ip ospf summary-address
Displays OSPF summary-address redistribution information.