Chapter 14. Understanding Border Gateway Protocol Version 4 (BGP-4)

This chapter covers the following key topics about Border Gateway Protocol version 4 (BGP-4):

• BGP-4 protocol specification and functionality

• Neighbor relationships

• Advertising routes

• Synchronization

• Receiving routes

• Policy control

• Scaling IBGP networks (route reflectors and confederations)

• Best-path calculation

An autonomous system (AS) is a set of devices under common administration. Between two or more autonomous systems, the Border Gateway Protocol advertises network reachability information. The Internet backbone relies solely on BGP to announce and receive IP prefixes, and the only routing protocol that runs between two autonomous systems is BGP.

Before BGP, ...

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