BGP Terminology

BGP Terminology
Make sure you’re familiar with the following BGP terminology for the BSCI exam:
Autonomous system
An autonomous system was originally defined as a set of devices under
the same administrative control that used a single IGP for intra-AS routing and an EGP for inter-
AS routing. With the rapid changes that have occurred over the years, the definition of an autonomous
system has changed. An
autonomous system (AS)
is now considered to be a set of devices
under the same administrative control with one or more IGPs controlling intra-AS routing and
an EGP for inter-AS routing. Even though an autonomous system may have multiple IGPs operating
at the same time, the autonomous system will appear to other autonomous systems as having
one coherent interior routing plan. This allows the existence of multiple IGP autonomous
systems (EIGRP 100 and EIGRP 200, for example), which are really not the same as EGP autonomous
systems, within the same EGP AS.
BGP speaker
Any routing device that is running a BGP routing process is known as a
BGP speaker
.
Peers
When two BGP speakers form a TCP connection between them they are known as
peers
.
The term neighbor is the same as the term peer.
eBGP
External Border Gateway Protocol (eBGP)
is the routing protocol used to exchange
routing information between BGP peers in different autonomous systems.
iBGP
Internal Border Gateway Protocol (iBGP)
is the routing protocol used to exchange
routing information between BGP peers in the same autonomous system.
Inter-AS routing
Inter-AS routing
is routing that occurs between different autonomous systems.
Intra-AS routing
Intra-AS routing
is routing that occurs within the same autonomous system.
The terms defined in this section will appear throughout the next two chapters.
Now that you have some of the BGP terminology down, we can focus on how BGP
operates.