Using Access Lists In A Route Map; Configuration Example 1; Figure 4: Route Map Filtering - Juniper IP SERVICES - CONFIGURATION GUIDE V 11.1.X Configuration Manual

AS-path access list 2 is applied to routes that router London receives from router
Berlin. Router London rejects routes with the AS path 621 11 or 621 282 11.
Router London accepts routes with the AS path 282 11, 282 621, 282 621 11, or 282
11 621. However, it applies AS-path access list 3 to routes it forwards to router
Madrid, and filters out routes with the AS path 282 621 11 or 282 11 621.

Using Access Lists in a Route Map

You can use a route map instead of the neighbor filter-list command to apply access
lists for filtering routes.

Configuration Example 1

In Figure 4 on page 25, a route map is used to determine the weight for routes
learned by router Chicago.

Figure 4: Route Map Filtering

Access list 1 permits any route whose AS-path attribute includes 32 or 837. This
condition permits routes that originate in (or pass through from elsewhere) AS 32 or
AS 837. When these routes are advertised through AS 451 and AS 17 to router
Chicago, instance 1 of route map 1 matches such routes and sets their weight to 25,
overriding the neighbor weight set for updates received from 10.2.2.4.
Access list 2 permits any route whose AS-path attribute indicates that it originates
in AS 74. When these routes are advertised through AS 837 and AS 32 to router
Chicago, instance 1 of route map 2 matches such routes and sets their weight to 175,
overriding the neighbor weight set for updates received from 10.5.5.2.
The following example configures router Chicago:
host1(config)#router bgp 293
host1(config-router)#network 192.168.5.0 mask 255.255.255.0
host1(config-router)#neighbor 10.2.2.4 remote-as 17
host1(config-router)#neighbor 10.2.2.4 weight 150
Chapter 1: Configuring Routing Policy
Access Lists
25