0 EBGP AND IBGPIF AN AUTONOMOUS SYSTEM HAS MULTIPLE BGP SPEAKERS, IT...
2.0 EBGP and IBGP
If an Autonomous System has multiple BGP speakers, it could be used as a
transit service for other ASs. As you see below, AS200 is a transit
autonomous system for AS100 and AS300.
It is necessary to ensure reachability for networks within an AS before
sending the information to other external ASs. This is done by a
combination of Internal BGP peering between routers inside an AS and by
redistributing BGP information to Internal Gateway protocols running in
the AS.
As far as this paper is concerned, when BGP is running between
routers belonging to two different ASs we will call it EBGP (Exterior
BGP) and for BGP running between routers in the same AS we will call it
IBGP (Interior BGP).