Cisco Systems 3750E manual Configuring BGP Filtering with Route Maps, 38-54

Chapter 38 Configuring IP Unicast Routing

Configuring BGP

	Command	Purpose
Step 14
	show ip bgp	Verify the reset by checking information about the routing
	show ip bgp neighbors	table and about BGP neighbors.
Step 15
	copy running-config startup-config	(Optional) Save your entries in the configuration file.

Use the no form of each command to return to the default state.

Configuring BGP Filtering with Route Maps

Within BGP, route maps can be used to control and to modify routing information and to define the conditions by which routes are redistributed between routing domains. See the “Using Route Maps to Redistribute Routing Information” section on page 38-80for more information about route maps. Each route map has a name that identifies the route map (map tag) and an optional sequence number.

Beginning in privileged EXEC mode, follow these steps to use a route map to disable next-hop processing:

	Command	Purpose
Step 1
	configure terminal	Enter global configuration mode.
Step 2 route-map map-tag[[permit deny]		Create a route map, and enter route-map configuration mode.
	sequence-number]]
Step 3
	set ip next-hopip-address [...ip-address]	(Optional) Set a route map to disable next-hop processing
	[peer-address]	• In an inbound route map, set the next hop of matching routes to
		be the neighbor peering address, overriding third-party next hops.
		• In an outbound route map of a BGP peer, set the next hop to the
		peering address of the local router, disabling the next-hop
		calculation.
Step 4
	end	Return to privileged EXEC mode.
Step 5
	show route-map [map-name]	Display all route maps configured or only the one specified to verify
		configuration.
Step 6
	copy running-config startup-config	(Optional) Save your entries in the configuration file.

Use the no route-mapmap-tagcommand to delete the route map. Use the no set ip next-hopip-addresscommand to re-enable next-hop processing.

Configuring BGP Filtering by Neighbor

You can filter BGP advertisements by using AS-path filters, such as the as-pathaccess-listglobal configuration command and the neighbor filter-listrouter configuration command. You can also use access lists with the neighbor distribute-listrouter configuration command. Distribute-list filters are applied to network numbers. See the “Controlling Advertising and Processing in Routing Updates” section on page 38-88for information about the distribute-listcommand.

You can use route maps on a per-neighbor basis to filter updates and to modify various attributes. A route map can be applied to either inbound or outbound updates. Only the routes that pass the route map are sent or accepted in updates. On both inbound and outbound updates, matching is supported based on AS

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
38-54	OL-9775-02