BGP- Border Gateway Protocol

• It makes internet work.

• Standardized exterior gateway protocol

• Designed to exchange routing and reach ability of info b/w autonomous systems.

• Often classified as a path vector protocol.

• BGP makes routing decisions based on paths , n/w policies or rule – sets configured by a n/w administrator & is involved in making core routing decisions.

• BGP makes use of routing within an autonomous system(AS).

• It is one the most complex and difficult to configure protocol but its emphasis on security and scalability makes its usage essential.

1. Border Gateway Protocol (BGP) is an External Gateway Protocol (EGP), which means it is designed to act as a routing protocol on the edge of your network, passing routing information about the structure of your network behind your gateway router.

2. This information can then be sent on to other BGP routers, informing them which networks are found behind the BGP router. A BGP router announces routes that they have learned and can also retransmit routes learned from the IGPs found on their networks, as illustrated in the following figure.

3. BGP’s purpose is not only to exchange its information, but also to exchange network reachability and availability information for the Autonomous Systems (AS) paths with other BGP systems on the network. This process allows all systems to construct topology graphs of the entire network infrastructure on both sides of the BGP link.

4. This process also allows these systems to identify loops and other issues that may affect network performance and availability.