This is NOT a technical document on BGP, but a "cheat sheet" of terms and acronyms that pop up when discussing BGP. This is a growing document, and is nowhere near encompassing of all things BGP.

BGP Terms and Definitions

ARIN - American Registry for Internet Numbers: governing body for IP address distribution (
AS - Autonomous System: A set of routers that is administered by a single organization
ASN - Autonomous System Number: public AS number in RADB
BGP - Border Gateway Protocol: Routing protocol designed for interdomain routing
CIDR - Classless Inter-Domain Routing: Supernetting, a way of recognizing network numbers without the restraints of classes (Class A, B, C, etc.)
EBGP - External BGP: BGP routing between AS's
EGP - External Gateway Protocol
IBGP - Internal BGP: BGP routing within an AS
IGP - Internal Gateway Protocol: "language" that internal routers use to share routing tables (e.g. RIP, OSPF, etc.)
MED - (also known as Inter-AS_Metric) Multi-Exit Discriminator: attribute passed to neighbor routers defining the preferred path among multiple entry paths into an AS. A lower MED has precedence over a higher MED.
Neighbor - See Peer
Peer - (also known as Neighbor) a TCP-connected router that exchanges BGP routing information
RADb - Routing Assets Database: public routing database of networks on the Internet (

Useful BGP Information