BGP route refresh capability annoucement
The Route Refresh capability is one of several methods used to dynamically and yet efficiently request a re-advertisement of prefixes of BGP peers whenever a change in policy is enacted. The other methods are performing a manual hard reset on the BGP routers, or configuring BGP soft reconfiguration.
A BGP router informs its neighbors of its route refresh capability by including the “Route Refresh Capability” optional parameter in the OPEN message when establishing a BGP session with the neighbor. The OPEN message is the first message sent by a BGP router to its neighbor when establishing a BGP session, and it contains various parameters that are used to negotiate the BGP session. If the “Route Refresh Capability” optional parameter is included in the OPEN message, it indicates to the neighbor that the router supports the route refresh capability.