Concept Guide

Table Of Contents
Figure 19. BGP Routers in Full Mesh
The number of BGP speakers each BGP peer must maintain increases exponentially. Network management quickly becomes impossible.
Sessions and Peers
When two routers communicate using the BGP protocol, a BGP session is started. The two end-points of that session are called neighbors
or peers. A local device does not identify a BGP peer automatically. You have to manually congure the connections between BGP running
devices. BGP uses TCP connection to communicate with another BGP neighbor. After establishing a TCP connection between the peers,
each peer exchange route information with other peer.
Establish a Session
Information exchange between peers is driven by events and timers. The focus in BGP is on the trac routing policies.
In order to make decisions in its operations with other BGP peers, a BGP process uses a simple nite state machine that consists of six
states: Idle, Connect, Active, OpenSent, OpenConrm, and Established. For each peer-to-peer session, a BGP implementation tracks which
BGP IP version 4 (BGPv4) Overview
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