Dictionary · Protocols and Ports
BGP
BGP — Border Gateway Protocol
Routing · Advanced
The routing protocol that exchanges reachability between autonomous systems on the Internet. Peers maintain a session on TCP 179 and apply policy to the routes they accept.
This is how independent networks tell each other which addresses they can reach. A bad announcement can send traffic the wrong way, so filters and monitoring matter.
Example: Two providers maintain a session and advertise their customer prefixes, with filters so a customer cannot announce the whole Internet.
Ports
- TCP 179 — Routing peer session
Common misconception
- It does not automatically choose the fastest path. It chooses using policy and attributes such as path length.