Cisco Systems 78-11741-02 manual Redistributing Routing Information, IPC-367

Configuring IP Routing Protocol-Independent Features

Redistributing Routing Information

protocols, the number of paths is controlled by the maximum-pathsrouter configuration command. The static route source can always install six paths. If more paths are available, the extra paths are discarded. If some installed paths are removed from the routing table, pending routes are added automatically.

When the traffic-share min command is used with the across-interfaceskeyword, an attempt is made to use as many different interfaces as possible to forward traffic to the same destination. When the maximum path limit has been reached and a new path is installed, the router compares the installed paths. For example, if path X references the same interface as path Y and the new path uses a different interface, path X is removed and the new path is installed.

To configure traffic that is distributed among multiple routes of unequal cost for equal cost paths across multiple interfaces, use the following command in router configuration mode:

Command	Purpose
Router(config-router)# traffic-share min	Configures multi-interface load splitting across different
{across-interfaces}	interfaces with equal cost paths.

Redistributing Routing Information

In addition to running multiple routing protocols simultaneously, the Cisco IOS software can redistribute information from one routing protocol to another. For example, you can instruct the software to readvertise IGRP-derived routes using RIP, or to readvertise static routes using the IGRP protocol. Redistributing information from one routing protocol to another applies to all of the IP-based routing protocols.

You also can conditionally control the redistribution of routes between routing domains by defining a method known as route maps between the two domains.

The following four tables list tasks associated with route redistribution. Although redistribution is a protocol-independent feature, some of the match and set commands are specific to a particular protocol.

To define a route map for redistribution, use the following command in global configuration mode:

Command	Purpose
Router(config)# route-map map-tag[permit deny]	Defines any route maps needed to control
[sequence-number]	redistribution.

One or more match commands and one or more set commands typically follow a route-mapglobal configuration command. If there are no match commands, then everything matches. If there are no set commands, nothing is done (other than the match). Therefore, you need at least one match or set command.

To define conditions for redistributing routes from one routing protocol into another, use at least one of the following commands in route-map configuration mode, as needed:

Command	Purpose
Router(config-route-map)# match as-pathpath-list-number	Matches a BGP autonomous system path access list.
Router(config-route-map)# match community-list	Matches a BGP community list.
community-list-number [exact]

Cisco IOS IP Configuration Guide

IPC-367