EGP

EGP is more commonly known as an External Gateway Protocol. This External Gateway Protocol was used extensively till the release of another routing protocol, named BGP, however, after the release of this BGP the use of this EGP decreased and today it is an obsolete routing protocol for the internet. It was originally specified in the 1982 by Eric C. Rosen. It was first specified in RFC 827 and then formally specified in RFC 904. During its time when it was being used, version 3 of the EGP was the most commonly used version for interconnecting autonomous systems moreover that was the last version of EGP.

EGP was used for exchanging routing information between the two neighbor gateway hosts in a network of autonomous systems or AS. The information was routed either in the same network or different networks. The main purpose of this external gateway protocol was to allow the exchange of the routing table information between the hosts that were connected to the internet. A routing table is basically a table which has information related to all the registered routers and the record of the addresses associated with them. Along with all this information there is also information regarding the metric cost associated with each of the router, to enable the best available route for the information to flow through.

The way the system work is that each router that is connected to the other polls its neighboring router and at the intervals between 120 to 480 seconds and then the neighbor router responds by sending its information table to the polling router. In this way the exchange of the tables take place and it helps in making the system efficient. External Gateways Protocol is based on the periodic polling using Hello/ I-H-U or I heard you message exchanges tom monitor the neighbor router’s response.