CISCO ENHANCED INTERIOR GATEWAY ROUTING PROTOCOL (EIGRP)
Enhanced Interior Gateway Routing Protocol (EIGRP) is the upgraded version of Cisco's Interior Gateway Routing Protocol (IGRP). The EIGRP convergence technology is based on an algorithm called the algorithm for diffusing updates (DUAL). The algorithm maintains a continuous loop-free operation during a route measurement and makes it possible to synchronize all devices involved in topology transition. EIGRP has three tables, First, Neighbor Table . Second, Toplogy Table . Third, Routing Table.
The picture above is the the design for applying the EIGRP Neighbor Table, Now please set the IP Address for R1 , R2 , and R3 , after you make the IP Address for each, you can run command for three tables EIGRP, follow the command below,
hostname R1
int e0/0
ip addr 172.16.12.1 255.255.255.0
no shutdown
router eigrp 1
auto-summary
network 172.16.12.0 0.0.0.255
do show ip eigrp neighbor
do show ip eigrp topology
do show ip eigrp route eigrp
hostname R2
int e0/0
ip addr 172.16.12.2 255.255.255.0
no shutdown
int e0/1
ip addr 172.16.23.2 255.255.255.0
no shutdown
router eigrp 1
auto-summary
network 172.16.12.0 0.0.0.255
network 172.16.23.0 0.0.0.255
do show ip eigrp neighbor
do show ip eigrp topology
do show ip eigrp route eigrp
hostname R3
int e0/0
ip addr 172.16.23.3 255.255.255.0
no shutdown
router eigrp 1
auto-summary
network 172.16.23.0 0.0.0.255
do show ip eigrp neighbor
do show ip eigrp topology
do show ip eigrp route eigrp
By default, Routers communicate with each other using Multicast. If the network does not support Multicast. So, the Multicast cannot be transmitted smoothly for some reasons, the Router cannot become a Neighbor. In these situations, we use the Neighbor command to use Unicast to transmit EIGRP packets. You have to remember to confirm whether Neighbor is successfully established, you can use commands
show ip eigrp nieghborsYou can see the result on the picture below,EIGRP - HOLD TIME
EIGRP has two Timers, which are Hello Timer and Hold Timer. The default value of Hello is 5 seconds and the default value of Hold is 15 seconds, which means that EIGRP Router will send Hello Message every 5 seconds. If it receives it, it will maintain the Neighbor relationship. Discontinue the Neighbor relationship.Therefore, the Hold Timer will count down from 15 seconds until it counts down 15 seconds after receiving Hello. Hello Timer and Hold Timer can be changed under interface, Now run the command below at Router2 and see also the picture result,
int e0/0
ip hello-interval eigrp ?
ip hello-interval eigrp 1 ?
ip hello-interval eigrp 1 10
ip hold-time eigrp ?
ip hold-time eigrp 1 ?
ip hold-time eigrp 1 30
clear ip eigrp 1 neighbors
EIGRP - AUTHENTICATION
Set a password between the interfaces of EIGRP Neighbor, so as to prevent Router from pretending to be Neighbor to steal Router information and also set Key Chain and MD5 encryption on the interface, Run the command below at R1 and R2,
key chain MyChain
key 1
key-string MyPassword
int e0/1
ip authentication key-chain eigrp 1 MyChain
ip authentication mode eigrp 1 md5
do sh ip eigrp int detail
See the picture result below,