Applying Filters Provided by BGP Peers to Outbound Routes
You can configure a BGP peer to accept route filters from remote peers and perform outbound route filtering using the received filters. By filtering out unwanted updates, the sending peer saves resources needed to generate and transmit updates, and the receiving peer saves resources needed to process updates. This feature can be useful, for example, in a virtual private network (VPN) in which subsets of customer edge (CE) devices are not capable of processing all the routes in the VPN. The CE’s can use prefix-based outbound route filtering to communicate to the provider edge (PE) routing device to transmit only a subset of routes, such as routes to the main data centers only.
To configure prefix-based outbound route filtering, include the following statements:
For a complete list of hierarchy levels at which you can configure these statements, see the statement summaries for these statements.
 | Note: The maximum number of prefix-based outbound route filters that a BGP peer can accept is 5,000. If a remote peer sends more than 5,000 outbound route filters to a peer address, the additional filters are discarded and a system log message is generated. |
You can also enable interoperability with routing devices that use the vendor-specific compatibility code of 130 for outbound route filters and the code type of 128. The standard code is 3, and the standard code type is 64. You can configure interoperability for the routing device as a whole or for specific BGP groups or peers only.
To configure BGP peers to interoperate with routing devices that use vendor-specific compatibility codes for outbound route filters, include the bgp-orf-cisco-mode statement:
