The Border Gateway Protocol (BGP) is an exterior gateway protocol (EGP) used primarily to establish point-to-point connections and transmit data between peer ASs. Unlike the IGPs RIP, OSPF and IS-IS, BGP must explicitly advertise the routes between its peers. The route advertisements determine prefix reachability and the way packets are routed between BGP neighbors. Because BGP uses the packet path to determine route selection, it is considered a path-vector protocol.
This overview contains the following topics: