Enabling BGP Route Target Filtering

You can limit the number of prefixes advertised on BGP peerings specifically to the peers that need the updates.

In a VPN provider network, a BGP speaker advertises all VPN routes to the peers in the same VPN. Peers that are configured either as a route reflector or border router for a VPN must store all routes within the network. While PE routers automatically discard routes that do not affect them, these route updates must still be generated and received.

Enabling route target filtering allows you to limit these route updates.

To enable route target filtering, include the route-target statement:

For a list of hierarchy levels at which you can include this statement, see the statement summary section for this statement.

If you include the advertise-default statement, the router advertises the default route-target route (0:0:0/0) and suppresses any specific route-target routes. This is useful for a route reflector in a BGP group consisting of neighbor PE routers only. If you include the external-paths statement, the router limits the number of external paths accepted for route filtering. The range is from 1 through 256. The default is 1. If you include the teardown statement, the session is torn down when the maximum number of prefixes is reached. If you specify a percentage, messages are logged when the number of prefixes reaches that percentage. Once the session is torn down, it is reestablished in a short time. Include the idle-timeout statement to keep the session down for a specified amount of time, or forever. If you specify forever, the session is reestablished only after you use the clear bgp neighbor command.

For more information about VPNs, see the Junos VPNs Configuration Guide.