Exterior Gateway Protocol (EGP)

If you are following this weblog, then you might have already read our previous post where we introduced the Interior Gateway Protocol. if I may recall, for both our new readers and those who read the previous weblog, we stated that the routing protocols could be classified according to their various characteristics which are purpose, operation, and behavior. We also stated that the routing protocols are divided into the interior gateway protocol IGP and exterior gateway protocol EGP according to their purpose.

As we have already explained the Interior Gateway Protocol, we will be discussing the Exterior Gateway Protocol in this post.

What is Exterior Gateway Protocol

Unlike Interior Gateway Protocol, the exterior gateway protocol is used to share the routing information in-between different autonomous systems. These routing information’s are simply the information by which networks could be accessed through certain autonomous systems.  

The EGP routers are configured at the edge of the network. They announce that they can reach networks that are part of its autonomous system. The systems first exchange EGP Hello and I-Heard-You (I-H-U) messages before exchanging routing information. These messages provide the basis of a communication channel between two EGP gateways. The exchange of Hello and I-H-U messages is known as acquiring a neighbor, and computers communicating over EGP are known as EGP neighbors.

One of the most popular Exterior Gateway Protocols used on the Internet is the Border Gateway Protocol (BGP).