Cooperative BGP4 Route Filtering

By default, the device filters incoming routes locally, on the device itself. With cooperative BGP4 route filtering, the neighbor performs the filtering before sending the routes to the device. For example, the device sends a deny filter to a neighbor, which the neighbor uses to filter out updates before sending them to the device. The neighbor saves the resources it would use to generate the route updates, and the device saves the resources it would use to filter the routes.

When you enable cooperative filtering, the device advertises this capability in its OPEN message to the neighbor. The OPEN message also indicates whether the device is configured to send filters, receive filters, or both, and the types of filters it can send or receive. The device sends the filters as Outbound Route Filters (ORFs) in ROUTE REFRESH messages.

The following is the high-level process for configuring cooperative filtering on the device and on the BGP4 neighbor.

Configure the filter. Cooperative filtering is currently supported only for filters configured using IP prefix lists.
Apply the filter as an inbound filter to the neighbor.
Enable the cooperative route filtering feature on the device. You can enable the device to send ORFs to the neighbor, to receive ORFs from the neighbor, or both. The neighbor uses the ORFs it receives as outbound filters when it sends routes to the device. Likewise, the device uses the ORFs it receives from the neighbor as outbound filters when sending routes to the neighbor.
Reset the BGP4 neighbor session to send and receive ORFs.
Perform these steps on the other device.

Note

If the device has inbound filters, the filters are still processed even if equivalent filters have been sent as ORFs to the neighbor.