BGP (Border Gateway Protocol) is a routing protocol used to exchange network path information across the internet. Routing protocols can generally be categorized into two main types: Interior Gateway Protocols (IGP), used within an individual organization or site, and Exterior Gateway Protocols (EGP), designed specifically for exchanging routing information between different organizations. While protocols like OSPF (Open Shortest Path First) and RIP (Routing Information Protocol) belong to the IGP category, BGP belongs to the EGP category and is currently the most widely adopted protocol for inter-AS routing.
In BGP terms, an "organization" typically refers to an Autonomous System (AS), making BGP specifically an "inter-AS routing protocol." Border routers, placed at network boundaries between internal networks and external networks, commonly employ this protocol.
Technically, BGP peers communicate using TCP on port 179. Routers exchanging BGP routing information with each other are called "neighbors" or "peers." After establishing sessions, BGP peers first exchange basic identification parameters followed by complete routing information each peer has available. Subsequently, routers exchange periodic KEEPALIVE messages to confirm connectivity. When route changes occur in routing tables, only incremental route updates are exchanged, minimizing network overhead.
Additionally, F5 provides an optional Enhanced Routing Module supporting BGP functionality for its BIG-IP product range.