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EIGRP
ENHANCED INTERIOR GATWAY PROTOCOL
OBJECTIVES:

Describe the background and history of Enhanced
Interior Gateway Routing Protocol (EIGRP).

Define EIGRP Terminology.

explain control packets in EIGRP

Calculate the composite metric used by EIGRP.

Describe the concepts and operation of DUAL.
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EIGRP

It is an enhancement of IGRP.

Hybrid routing protocol (distance vector + link-state)

Developed in 1985 to overcome RIPv1’s limited hop count.

Was an cisco proprietary routing protocol till 2013, now open standard.

Classless protocol.

Symbol in routing table is ‘D’.

Administrative distance = 90.

Fast convergence : use DUAL.

METRIC is determined by (B.W, delay, load, and reliability).

Max hop count = 224.

Support multiple network layer protocol ( IP, IPX, AppleTalk).

Uses multicast address 224.0.0.10
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EIGRP TERMINOLOGY

Neighbor table:table contain all neighbors.

Topology table:table contain all routes to all networks.

Routing table:-
table contain the best route to all networks.

Successor:best route.

Feasible successor:backup for best route.
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control packets in EIGRP

Hello packet:–
used to discover & form adjacencies with neighbors, UDP, Multicast.

Query packet:ask neighbors about routing information, TCP, Unicast/ Multicast.

Update packet:send routing update, TCP, Unicast/ Multicast.

Reply packet:-
respond to the query packet, TCP, Unicast.

Acknowledgment packet:used to acknowledge receipt of update, query & reply packets , UDP,
Unicast.
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METRIC
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
Composite metric

metric = [ K1 * bandwidth + (K2 * bandwidth)/256 - load) + K3 *
delay] * [ K5/(reliability + K4)]

It don’t consider single criteria to calculate the metric but uses
numbers of criteria which includes bandwidth, load, delay,
reliability, and maximum transfer unit (MTU).

K value for B.W and delay by default equal to 1, and other values
of k is zero.

metric = [ K1 * bandwidth + K3 * delay]
DIFFUSION UPDATE ALGORITHM(DUAL)

This algorithm stores neighbor’s routing information in a local
topology table.

If a primary route in the routing table fails, Dual can take a
backup path from the topology table and place it in the
routing table.

If no backup route is found in the topology table, it will
generate a query packet sent to the neighbor.
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