Monday, 27 November 2017

Enhanced Interior Gateway Routing Protocol (EIGRP)

Enhanced Interior Gateway Routing Protocol (EIGRP)

EIGRP is a classless protocol, and thus supports VLSMs
EIGRP applies an Administrative Distance of 90 for routes originating within the local Autonomous System

EIGRP uses Bandwidth and Delay of the Line, by default, to calculate its distance metric
EIGRP has a maximum hop-count of 224.
Calculates its best path on bandwidth and delay
Formula (10^7/bandwidth + delay/10) *256
Serial 20000 ms (delay)
FE 1000 ms (delay)
E 10000 ms (delay)

EIGRP Table:-

Builds three separate tables: -
Neighbor table – list of all neighboring routers. Neighbors must belong to the same Autonomous System 
Topology table – list of all routes in the Autonomous System •
Routing table – contains the best route for each known network


EIGRP forms neighbor relationships, called adjacencies, with other routers in the same AS by exchanging Hello packets. Only after an adjacency is formed can routers share routing information.
Default time of hello packet is 5 sec.

Best path is called SUCCESSOR
Value of best path is called FEASIBLE DISTANCE (FD)
Backup path is called FEASIBLE SUCCESSOR (FS)
ADVERTISE DISTANCE- value of neighbour upto destination
Condition for backup path- router choses best path only if AD<FD

EIGRP Packet Types:-

Hello packet- after every 5 sec

UPDATE PACKET – WHENEVER CHANGES OCCUR IN NETWORK


QUERY PACKET – when a router have no best path as well as backup path


REPLY PACKET – IF requested routers have further path to go then they reply back to router as reply packet.

EIGRP router states :-

ACTIVE STATE – when router have no successor and feasible successor
PASSIVE STATE – when router have its both successor and feasible succesor
STUCK IN ACTIVE – when router have no path to go to destination

EIGRP Syntax:-

Like RIP , EIGRP also use directlly connected network
R(config) # router eigrp (10)
R(config) # network 10.0.0.0
R(config) # network 20.0.0.0
Here , 10 is an autonomous number. Eigrp forms neighborship on the basis of A.N.
Autonomous number is locally defined on each router
Without autonomous no. EIGRP couldn’t be configured 

Commands:-
Sh ip route (best path)
Sh ip eigrp topology (chk alternative paths and router state ) 
Sh ip eigrp neighbor (chk neighbors)








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