Cisco Systems 3750E manual Configuring Policy-Based Routing, 38-83

Chapter 38 Configuring IP Unicast Routing

Configuring Protocol-Independent Features

Beginning in privileged EXEC mode, follow these steps to control route redistribution. Note that the keywords are the same as defined in the previous procedure.

	Command	Purpose
Step 1
	configure terminal	Enter global configuration mode.
Step 2 router {bgp rip ospf eigrp}		Enter router configuration mode.
Step 3 redistribute protocol [process-id]{level-1 level-1-2		Redistribute routes from one routing protocol to
	level-2} [metric metric-value][metric-type type-value]	another routing protocol. If no route-maps are
	[match internal external type-value] [tag tag-value]	specified, all routes are redistributed. If the keyword
	[route-map map-tag] [weight weight] [subnets]	route-mapis specified with no map-tag, no routes are
		distributed.
Step 4
	default-metric number	Cause the current routing protocol to use the same
		metric value for all redistributed routes (BGP, RIP and
		OSPF).
Step 5
	default-metricbandwidth delay reliability loading mtu	Cause the EIGRP routing protocol to use the same
		metric value for all non-EIGRP redistributed routes.
Step 6
	end	Return to privileged EXEC mode.
Step 7
	show route-map	Display all route maps configured or only the one
		specified to verify configuration.
Step 8
	copy running-config startup-config	(Optional) Save your entries in the configuration file.

To disable redistribution, use the no form of the commands.

The metrics of one routing protocol do not necessarily translate into the metrics of another. For example, the RIP metric is a hop count, and the IGRP metric is a combination of five qualities. In these situations, an artificial metric is assigned to the redistributed route. Uncontrolled exchanging of routing information between different routing protocols can create routing loops and seriously degrade network operation.

If you have not defined a default redistribution metric that replaces metric conversion, some automatic metric translations occur between routing protocols:

•RIP can automatically redistribute static routes. It assigns static routes a metric of 1 (directly connected).

•Any protocol can redistribute other routing protocols if a default mode is in effect.

Configuring Policy-Based Routing

You can use policy-based routing (PBR) to configure a defined policy for traffic flows. By using PBR, you can have more control over routing by reducing the reliance on routes derived from routing protocols. PBR can specify and implement routing policies that allow or deny paths based on:

•Identity of a particular end system

•Application

•Protocol

You can use PBR to provide equal-access and source-sensitive routing, routing based on interactive versus batch traffic, or routing based on dedicated links. For example, you could transfer stock records to a corporate office on a high-bandwidth, high-cost link for a short time while transmitting routine application data such as e-mail over a low-bandwidth, low-cost link.

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-02		38-83