The external update process is concerned with the distribution of routing information to BGP speakers located in neighboring autonomous systems. As part of Phase 3 route selection process, the BGP speaker has updated its Adj-RIBs-Out and its Forwarding Table. All newly installed routes and all newly unfeasible routes for which there is no replacement route shall be advertised to BGP speakers located in neighboring autonomous systems by means of UPDATE message.
Any routes in the Loc-RIB marked as unfeasible shall be removed. Changes to the reachable destinations within its own autonomous system shall also be advertised in an UPDATE message.