What is EIGRP and how to Configure EIGRP

What is EIGRP

When you’re running a much better routing protocol put “E” in front of IGRP because Cisco no longer supports IGRP. EIGRP (Enhanced IGRP) provides an edge over Cisco-proprietary protocol, and IGRP (Interior Gateway Routing Protocol). EIGRP is an enhanced distance-vector routing protocol and is classless. The concept of autonomous systems, that EIGRP uses to describe the set of contiguous routers that share routing information and run the same routing protocol.

The routing updates contain the subnet mask information in EIGRP, unlike IGRP. When designing our networks, the subnet advertisement information allows us to use VLSM (Variable Length Subnet Mask) and summarization.

EIGRP has the characteristics of Link-state and distance-vector routing protocols and is sometimes referred to as a hybrid routing protocol. Like OSPF, EIGRP doesn’t send link-state routing updates instead; it sends traditional distance-vector routing updates which contain information about networks plus the cost of reaching them from the router advertising. Between the neighbors, it synchronizes routing tables at startup and then sends specific updates when there is any change occurs in topology and for large networks, this makes the EIGRP more suitable.

The maximum hope count of EIGRP is 255 with the default being 100. Various powerful features make the EIGRP a real standout from other protocols and IGRP.

The main ones are listed below:

v Support IPv6 and IP via dependent modules protocol.
v Same as OSPF and RIPv2 it is considered classless.
v Support VLSM / CIDR.
v Support discontiguous networks and summaries.
v Efficient discovery of neighbors.
v Communication via RTP (Reliable Transport Protocol).
v The selection of the best path via DUAL (Diffusing Update Algorithm).

How to Configure EIGRP

How to Configure EIGRP

Configuring the Router R1 Interfaces

Router> enable

Router# configure terminal

Enter configuration commands, one per line. End with CNTL / Z.

Router (config) # hostname R1

R1 (config) # interface serial 0/1/0

OR

R1 (config) # int s 0/1/0

R1 (config-if) # ip address 192.168.2.1 255.255.255.0

R1 (config-if) #encapsulation hdlc

R1 (config-if) #clock rate 64000

R1 (config-if) #keepalive 12

R1 (config-if) #no shutdown

OR

R1 (config-if) #no shut

%LINK-5-CHANGED: Interface Serial0/1/0, changed state to down

R1 (config-if) #exit

R1 (config) # interface fastethernet0/0

OR

R1 (config) # int fa0/0

R1 (config-if) # ip address 192.168.1.10 255.255.255.0

R1 (config-if) #no shutdown

Interface Status up

R1 (config-if) #end

R1#

Configuring the Router R2 Interfaces

Router> enable

Router# configure terminal

Enter configuration commands, one per line. End with CNTL / Z.

Router (config) # hostname R2

R2 (config) # interface serial 0/1/0

OR

R2 (config) # int s 0/1/0

R2 (config-if) # ip address 192.168.2.2 255.255.255.0

R2 (config-if) #encapsulation hdlc

R2 (config-if) #keepalive 12

R2 (config-if) #no shutdown   

OR

R2 (config-if) #no shut

Interface Status up

R2 (config-if) #exit

R2 (config) # interface fastethernet0/0

OR

R2 (config) # int fa0/0

R2 (config-if) # ip address 192.168.4.10 255.255.255.0

R2 (config-if) #no shutdown

Interface Status up

R2 (config-if) #end

R2#

Router R1 and R2 Routing Table

Router R1

R1# show ip route

IP Route Status

Note: By default, in the router R1 routing table the two associated interfaces and directly connected networks are listed.

Router R2

R2# show ip route

IP Route Status

Note: By default, in the router R2 routing table the two associated interfaces and directly connected networks are listed.

Ping Verification on Router R1 and R2

Router R1

R1#ping 192.168.2.2

Successful Ping Verification

R1#ping 192.168.4.10

Unsuccessful Ping Verification

Note: The ping was not successful because the network 192.168.4.0 is not listed in the router R1 routing table. Using the EIGRP (Enhanced IGRP) the network 192.168.4.0 needs to be put in the R1 routing table.

Router R2

R2#ping 192.168.2.1

Successful Ping Verification

R2#ping 192.168.1.10

Unsuccessful Ping Verification

Note: The ping was not successful because the network 192.168.1.0 is not listed in the router R2 routing table. Using the EIGRP (Enhanced IGRP) the network 192.168.1.0 needs to be put in the R2 routing table.

Configuring EIGRP on Router R1 and R2

Router R1

R1#configure terminal

Enter configuration commands, one per line.  End with CNTL/Z.

R1 (config) #router eigrp?

<1-65535> Autonomous system number

R1 (config) #router eigrp 20

R1 (config-router) #network 192.168.2.0

R1 (config-router) #network 192.168.1.0

R1 (config-router) #end

R1#

Note: The autonomous number on EIGRP running routers must be the same so that they can share routing information.

Router R2

R2#configure terminal

Enter configuration commands, one per line.  End with CNTL/Z.

R2 (config) #router eigrp 20

R2 (config-router) #network 192.168.2.0

R2 (config-router) #network 192.168.4.0

R2 (config-router) #end

R2#

Router R1 and R2 Routing Table

Router R1

R1#show ip route

IP Route Status

R1#

Router R2

R2#show ip route

IP Route Status

R2#

Note: Metric value is 2172416. The administrative distance is 90 and the word “D” represents the EIGRP.

Ping Verification on Router R1 and R2

Router R1

R1#ping 192.168.4.10

Successful Ping Verification

Router R2

R2#ping 192.168.1.10

Successful Ping Verification

IP Protocol verification on Router R1

R1#show ip protocols

IP Protocol Status

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