HP ProCurve Secure Router 7203 dl Advanced Management And Configuration Manual page 707

IP Routing—Configuring RIP, OSPF, BGP, and PBR
Configuring BGP
After configuring the community list, create a route map entry:
ProCurve(config)# route-map ISPOut 10
Then enter this command:
Syntax: match community <listname>
N o t e
This command does not define a community for routes. It selects routes
according to their predefined community or communities. Other BGP neigh-
bors, either internal or external, should have placed the route in a community.
If you want to set other policies for the community, you must enter a set
command as described in "Prepending Private AS Numbers for Load Balanc-
ing" on page 13-96 and "Setting a Multi-Exit Discriminator Metric for Load
Balancing" on page 13-98. Otherwise, you should now apply the map to the
BGP neighbor as an outbound policy. (See "Applying a Route Map Entry to a
BGP Neighbor" on page 13-104.)
Filtering Advertised Routes According to AS Path. You can also filter
an advertised route according to the hops listed in its AS field. In this way, you
can attempt to influence which autonomous systems external neighbors can
access. For example, ISP routers can filter routes with paths that include
customer AS numbers to prevent themselves from advertising private cus-
tomer routes to unauthorized peers.
Private networks do not typically transit traffic between AS. Therefore, filter-
ing advertised routes according to AS path is usually unnecessary when
configuring eBGP in a private network.
To select routes according to values in their AS fields, first create the AS list:
Syntax: ip as-path-list <listname>
Then enter this command:
Syntax: [deny | permit] <string of AS numbers>
For example, you can permit the router to advertise only routes that use AS 1
and 2:
ProCurve(config-as-path-list)# permit 1 2
Remember that this statement only permits routes that use both AS 1 and AS
2. If you want to permit any routes that use either AS, you should enter
separate statements:
13-93