You use the BGP4+ Outbound Route Filtering (ORF) feature to minimize the number of BGP updates sent between BGP peers.
When ORF is enabled, unwanted routing updates are removed, reducing the amount of system resources required for generating and processing routing updates. The ORF feature is enabled through the advertisement of ORF capabilities to peer routers. The locally configured BGP4 inbound prefix filters are sent to the remote peer. The remote peer applies the filter as an outbound filter for the neighbor.
You can configure ORF with send and receive ORF capabilities. The local peer advertises the ORF capability in send mode, indicating that it will accept a prefix list from a neighbor and apply the prefix list to locally configured ORFs. Using send mode, the local peer exchanges the ORF capability with a remote peer for a prefix list that is configured as an inbound filter for that peer locally.
The remote peer sends the first update after it receives a ROUTE REFRESH request or BGP ORF with IMMEDIATE from the peer. The local and remote peers exchange updates to maintain the ORF on each router.