Border Gateway Protocol (BGP)

 

About

·       Border Gateway Protocol (BGP) is a standardized exterior gateway protocol designed to exchange routing and reachability information between autonomous systems (AS) on the Internet.

·       In simple word BGP is the routing method that enables the Internet to function. Without it, we wouldn’t be able to do a Google search or send an email. 

·       BGP is classified as a path-vector routing protocol, and it makes routing decisions based on paths, network policies, or rule-sets configured by a network administrator.

·       The Border Gateway Protocol was first described in 1989 in RFC 1105, and has been in use on the Internet since 1994.

·       BGP used for routing within an autonomous system is called Interior Border Gateway Protocol, Internal BGP (iBGP). In contrast, the Internet application of the protocol is called Exterior Border Gateway Protocol, External BGP (eBGP).

What’s the difference between external BGP and internal BGP?

·       Routes are exchanged and traffic is transmitted over the Internet using external BGP or eBGP. Autonomous systems can also use an internal version of BGP to route through their internal networks, which is known as internal BGP, or iBGP for short. It should be noted that using internal BGP is NOT a requirement for using external BGP. Autonomous systems can choose from a number of internal protocols to connect the routers on their internal network.

·       External BGP is like international shipping; there are certain standards and guidelines that need to be followed when shipping a piece of mail internationally. Once that piece of mail reaches its destination country, it has to go through the destination country’s local mail service to reach its final destination. Each country has its own internal mail service that doesn’t necessarily follow the same guidelines as those of other countries. Similarly, each autonomous system can have its own internal routing protocol for routing data within its own network.