EIGRP (Enhanced Interior Gateway Routing Protocol) is a classless, Cisco proprietary hybrid routing protocol that supports multiple protocols and uses an autonomous system numbering system. It features a reliable transport protocol (RTP) for neighbor discovery and table synchronization, and utilizes the Diffusing Update Algorithm (DUAL) for efficient routing and recovery. EIGRP maintains three tables for neighbor relationships, link-state information, and active routes, facilitating dynamic routing without traditional loop control methods.

1. EIGRP
Enhanced interior gateway routing protocol
Featuring EIGRP………….
Classless
Cisco proprietary
Autonomous system 1-65536
VLSM
Hybrid
hop count = 255
Support multiple protocols like IP, IPX, Apple
talk, Also IPv6.

2. EIGRP intro
Eigrp is a class les cisco proprietary protocol. It use concept of Autonomous
system to differentiate each part of the network using a specific number
from 1-655536.
It also support the VLSM technique to save more IP`s for an
internetwork.
It is a hybrid routing protocol due to the features of both
the DISTANCE VECTOR+LINK STATE.
Eigrp is not able to send the link state
update packets like the OSPF but it can send the distance vector update
containing the information about the networks.
But EIGRP have some link state
characteristics like it can synchronize the routing tables between the
neighbors at startup and also use TRIGGER update

3. EIGRP intro
Maximum hop counts by the EIGRP is 255.
And it can also route multiple protocols like IP,IPX,APPLE TALK
etc.
It has also the Metrix like
Bandwidth
load
Delay
Reliability
MTU.
Also there is no LOOP control method is required for the EIGRP

4. EIGRP modules..
RTP:- Reliable transport protocol
It is use to create the neighbor ship tables in the
router and Distributing the LSA{( Link state Advertisement) information about
any link to the all connected routers with that interface} .
RTP send a hello packet to
all the neighbors and when the neighbors will reply with acknowledgement
packet then it will create a NEIGHBOUR TABLE.
for the RTP processes the EIGRP use the
Multicast addresses from the D class {224.0.0.9}.
Eigrp maintain the neighbor table of all its
neighbors using the RTP and if there is any router which is not sending any
update about it then RTP use multicast update for that router for 15 times and
if the router will not make any reply then after the 16th update that router is
assumed as unreachable and removed from the neighbourship table

5. EIGRP DUAL
DUAL:- Diffusing Update Algorithm
it is the Algorithm which enables the
EIGRP to use the DISTANCE VECTOR + LINK STATE methods
simultaneously.
like 1.VLSM
2.Backup route are possible.
3.Send route Queries to the neighbors if the
Destination of the received packet is
unknown.
4.Dynamic route Recovery

6. EIGRP terms..
Reported distance:-
it is the Distance between the destination network and the next
hop IP address.
Feasible distance :-
It is the total distance between the destination and our router.
Successor:-
It is the Route with least hop count and listed as the primary
route in the routing table
Feasible successor:-
It is the backup route which can be used in case when the
primary route is not available or failed

7. EIGRP tables
EIGRP use three tables to store the all information's
1. Neighbourship table
2. LSA table
3. Routing table

8. EIGRP tables
1.Neighborship table:-
used to store the information about the routers with whom
neighbor ship relation is found.
2. LSA/Topology table:-
used to store the information about the every device in
every route in the internetwork by the information received from each
neighbor table.
3. Routing table:-
store the Routes which are currently used to store the
routing decisions.

9. EIGRP scenario

10. EIGRP configuration
Router_A(config)#router eigrp 10
Router_A(config_router)# network 10.0.0.4
Router_A(config_router)# network 10.0.1.0
Router_A(config_router)#exit
Router_A#wr
Router_B(config)# router eigrp 10
Router_B(config_router)# network 10.0.0.4
Router_B(config_router)# network 10.0.2.0
Router_B(config_router)# exit
Router_B#wr

11. EIGRP verification
#Show Ip route
#show ip route eigrp
#show ip eigrp neighbour
#show ip eigrp topology

12. EIGRP neighbor explanation
#show ip eigrp neighbor
H Add/interface hold uptime SRTT RTO Q Seq
(ms)
0 192.168.10.6 12 0:31:60 26 200 0 7
H= it indicates in which order neighbor is discovered
Hold= how long this route will wait for hello packet to arrive from the specific
neighbor.
Uptime= for how long the neighbor is connected.
SRTT= process of multicasting and unicasting.
RTO= Retransmission time out= maximum time for which EIGRP waits before
retransmitting a packet to neighbor.
Q= it indicates that my massage is In the queue.
Seq= sequence number of the last update from the neighbor

13. EIGRP end.

14. EIGRP