Introduction

EIGRP which means Enhanced Interior Gateway Routing Protocol is a routing protocol created by Cisco in order to improve IGRP protocol and make it more stable. This protocol is only compatible with Cisco products. EIGRP uses DUAL algorithm which was developed by SRI International.

Characteristics of EIGRP procotol

EIGRP uses a hybrid routing based on distance vector and link state. The metrics used by EIGRP are mainly the bandwidth, memory and processors overload.

EIGRP routers will save in its memory all the neighbours routing tables which allows to find quickly an other route in case of a network failure. If there is any route to reach a given destination, the router will send a request to its neighbours to find a way to send the packet instead. These neighbours request will be repeated until a route is found. EIGRP does not make periodic updates of these tables, which might seem to be a handicap. If a route change for any reason, the router using EIGRP will not be warned as fast as routers using other protocols. But if the EIGRP routers do not allow to make periodic updates, it allows them to send partial updates when the distance for a route changes.

This will allow EIGRP to save bandwidth traffic. By default, EIGRP uses 50% of the available bandwidth on a network. This value can be changed but the risks of packets loss will increase.

Routed protocols by EIGRP

EIGRP is able to route multiple protocols as AppleTalk, IP and IPX.

AppleTalk : To redistribute routes learned by the AppleTalk protocol, EIGRP uses RTMP (Routing Table Maintenance Protocol)

IP : With IP protocol, EIGRP uses OSPF, RIP, EGP, BGP to distribute information.

IPX : EIGRP uses Novell RIP to distribute information

If EIGRP is better than IGRP is that it uses recent technology and more important tech. Indeed, EIGRP is based on four important technologies.

- Neighbour Discovery / Recovery : Enables you to find the routers directly connected to