Enhanced Interior Gateway Routing Protocol

EIGRP (Enhanced Interior Gateway Routing Protocol) it is derived from IGRP

IGRP is a Distance vector routing protocol.

·         EIGRP is a Hybrid (or) Advance distance vector routing protocol

·         The AD value of EIGRP is

·         90     (EIGRP-INTERNAL),

·          170     (EIGRP-EXTERNAL)

·         Protocol  number is 88

·         It works on RTP (Reliable transport protocol)

·         It is fast convergence

·         It works as class full/ classless (no auto summary)

·         It works on AS number  (Autonomous system)  {in order to form neighbor ship the AS number should match}

·         Fast convergence

·         100% loop Free

·         Load balance across equal and unequal load balancing

·         Manual summarization at any point

Timers…..

Hello – 5 sec

Hold down timer – 15 sec 

EIGRP will works on multicast address 224.0.0.10

Neighbor Requirements for EIGRP

·         The Router must be able to send/receive IP packets to one another

·         Interface primary IP address must be in same subnet

·         Must not be passive on the connected interfaces

·         Must use same AS on the router configuration command

·         Must pass neighbor authentication (if configured)

·         K-values must match

EIGRP calculates Metric by K-values:

*K1 - bandwidth

K2 - load

*K3 - delay

K4 - reliability

K5 – reliability

 *** Least metric values will be preferred

Feasible condition:

Advertised distance: it is the distance between the neighbors to the destination

Feasible distance: it is the distance between sender to the destination

Note: when FD value ≥ AD value. Then no loop will be formed

Diffusion Update Algorithm (DUAL)  : This Algorithm will calculate the FD and AD values

Successor  : It is the best path, the shortest path to reach destination. It will stores in the routing table.

Feasible Successor  : It is next best path to reach destination. It will stores in the IP EIGRP routing table. Whenever Successor will down then this Feasible successor will become Successor path. It is a backup path

We can convert a feasible successor to a successor by changing the variance value.

Router(config)#router eigrp 10

Router(config-router)#no autosummary

Router(config-router)#variance ?

  <1-128>  Metric variance Multiplier

Packets Type:

·         Hello à Advertise to know the EIGRP Neighbours

·         Updates à Exchanges the routes information

·         Acknowledgement à Reply to updates

·         Query àAsk neighbours about routing information

·         Reply àRespond to query about routing information

·         Ack à Acknowledgment a reliable packets (to all communication link updates/ query/ reply etc.)

Eigrp Tables:

Ø  Neighbour Table

Ø  Topology table

Ø  Routing table

Within the Internet, an autonomous system (AS) is a collection of connected Internet Protocol (IP) routing prefixes under the control of one or more network operators that presents a common, clearly defined routing policy to the Internet.