What is BGP?
BGP is a protocol for exchanging routing information between autonomous networks in order to find the shortest routes for network traffic
- An AS - is an automonous system which is a logical abstraction of a network
- AN ASN is autonomous system which uniquely identifies an autonomous system
- ASNs are allocated by IANA and are allocated in the range 0-65535, where 64512 to 65534 are private
- iBGP is internal BGP - routing within an AS
- eGBP is external BGP - routing between ASs
How Does it Work?
- BGP operates over port 179 using flow control and error correction so it is reliable.
- Peering must be configurable manually and once set up if communicates network topology to other connected ASs.
- BCP exchanges the best path information between peers measured in number of hops (path length) and not latency - the path is called ASPATH
- You can artificially increase the path length to influence BGP not to take that path, e.g. a satellite link, e.g change path for 200,i to 200,200,200,i will case any 2 hop path to be chosen over this path