Enhanced Interior Gateway Routing Protocol (EIGRP) - A Detailed Overview

One of the fastest routing protocols in the world which come under the umbrella of IGP   interior gateway protocol. These are the protocols which are designed to work under same AS number, as is the group of a router which is managed by a single organization. After  reading this blog, you will have the basic idea about the EIGRP.

• The EIGRP replaced the interior gateway routing protocol in 1993 mainly due to changing structure of the IPV4 and introduction of classless IPV4 addressing.
• EIGRP support classless internet protocol addressing, VLSM, AND SUMMARIZATION.
• EIGRP has 2 metric to calculate the best path Vector metric and composite metric. The vector metric uses the hop count and the MTU and the composite metric which comprises of the five k values or modifiers used in a formula that gives us a metric value by default uses the composite metric.

• TheEIGRP is more scalable than rip as it goes beyond the 15 hop count and can go up to 100 by default.
• It has an advantage over OSPF i.e. it can do the unequal cost load balancing using the variance option, by default it can do the equal cost load balancing up to a maximum of 4 paths in EIGRP.
• It has three components, automatic neighbor discovery, reliable transmission protocol, and DUAL algorithm.
• It uses the hello message just like the link state routing protocol for the maintaining and discovering of neighbor but IT hello packet is different from OSPF. The EIGRP hello message consists of 5 k-values or modifiers and the MTU. These k values need to match by both the neighbor and the default values of k values that are 1,0,1,0,0

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• The Reliable transmission protocol is used for the reliable delivery of packet

• DUAL- the diffusing update algorithm run by EIGRP router keeping track of route advertise by the neighbor and calculate the best next hop to get to the destination using metric value. This path is known as a successor and the next best route is a feasible successor.
• All the router running the EIGRP uses the multicasting address of 224.0.0.101 for communication.
• In 2013, the EIGRP is converted into open standard from cisco propriety.
• The administrative value of EIGRP is 90 for internal routes and 170 for external routes and for summary routes it is 5

Structure of EIGRP

The EIGRP consist of 3 tables

Neighbor table -This table shows us the AS number, interface with which it is connected to the different neighbor. This can be shown by the command.

#sh ip EIGRP neighbor.

Routing table - This table consists of the successor or the best route to reach any destination. This table this can be shown by the command.

Download PDF Enhanced Interior Gateway Routing Protocol (EIGRP) - A Detailed Overview

#sh ip route

Topology table - This table consists of all the possible routes, the successor, and the feasible successor for reaching the destination. This table can be shown by

#sh ip eigrp topology

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