Intoroduction of EIGRP and how EIGRP works

Intoroduction of EIGRP

In this article we learn about the feature of EIGRP ,how EIGRP works and in the next part we learn the configuration of EIGRP for demotration purpose using packet tracer software.

Feature of EIGRP

EIGRP is called advanced distance vector and it is classless protocol. It is a standard protocol and use for cisco and non cisco device, but initially it was cisco proprietary. It is included all features of igrp. It supports upto 255 hop count and by default it supports upto 100 hop count.

Administrative distance of EIGRP is 90.It does not uses broadcast address .It only uses multicast and unicast address.

By default EIGRP uses bandwidth and delay to calculate the metric calculation.

Type of EIGRP table

There are three types of tables which EIGRP protocol uses.

· Neighbour table

To show the neighbour table we use the below command.

#show ip eigrp neighbour

· Topology table

To show the topology table we use the below command.

#show ip eigrp topology

· Routing table.

To show the routing table we use the below command

#show ip route

How EIGRP works

In this section we learn how to EIGRP works.

Suppose we have two routers.

STEP1: when router1 is advertising its interface then it send a hello packet to router2 using 224.0.0.10 multicast address. Router2 can not understand the the message unless it advertise its interface. After router2 advertises ites interface it also send a hello message to router1 using unicast address. After exchanging hello messages they build a neighbour table.

STEP2: After established the neighbour table they exchange their routing information to each other and select the all best path and build a topology table.

STEP3: After completing step2 they chose the top best route among the best routes and build a routing table.