EIGRP (ENHANCED INTERIOR GATEWAY ROUTING PROTOCOL)

EIGRP is the Cisco proprietary protocol 

Metric = Bandwidth + delay  (32 bit for the metric )

Bandwidth = (10000000/bandwidth) * 256

Delay = ( delay /10 ) * 256

Metrics are follows :- 
1.Bandwidth
2.Delay
3.Reliability
4.Load

Its is a classless routing protocol . Hop count is 255 (default is 100).

Routing table metric = Slowest bandwidth + sum of all delays 

Bandwidth :- 
T1 = 1554K
FE = 10000K
E = 10000K

Delay :-
T1 =20000mS
FE =100mS
E = 1000mS

In EIGRP outside routes (from distributed routes ) are tagged as external routes.
Automatic redistribution between EIGRP and IGRP if its both are same AS.

Metric = K1 * bandwidth + (K2 * bandwidth) / (256 -Load) + (k3 * delay ) + (k5/( reliability * k4)


 
Q. What is the Metric ( cost ) for 192.168.72.0/24 from ROUTER B.

Cost = slowest bandwidth + sum of delays.

= 1,657,856 +
      512,000 +
          2560 
___________
    2172416  

If you look at the routing table you will able to see




EIGRP will do the unequal cost load balancing .

EIGRP TABLES
1.Neighbor  Table :- Keeps all adjacent routers (neighbors) . Protocol wise separate table is there . 
ROUTER# show ip eigrp neighbors

2.Topology Table :- Keeps all the learned routes .Protocol wise separate table is there .(from distribution )
ROUTER# show ip eigrp topology

3.Routing Table :- Keeps the best routes from topology table to all destination.
ROUTER# show ip route


Successor : Easiest route to one destination. Keep in routing table. One or more successor may have to one destination.

Feasible Successor : Backup route for the successor. Keep in topology table.May have one or more FS to same destination.


Key Technologies of EIGRP :

Neighbor discover and recovery
Reliable Transport Protocol
Dual finite state machine
protocol specific modules

EIGRP Packet types :

1.Hello
2.Acknowledgement
3.Update
4.Query
5.Reply

 By default in EIGRP hold time is three times of hello interval.

Less than T1 (1554K) =  Hello interval 5 secs  Hold time = 15 secs

Greater T1 (1554K) =  Hello interval 60 secs  Hold time = 180 secs

If required we can modify the hello interval and hold time.
To form neighbors not required to match  hello and hold time at both ends.
In OSPF to make an neighbor need to match the hello and hold time .




There are three conditions needs to met then only neighborship will be established.

1. Hello or Ack received
2. AS numbers match
3. Identical metrics ( K Values )