EIGRP configuration

Configuring EIGRP 1

EIGRP configuration closely resembles RIP configuration. Only two steps are required:

  • enabling EIGRP by using the router eigrp ASN_NUMBER command
  • telling EIGRP which networks to advertise by using one or more network statements

 

The first command, router eigrp ASN_NUMBER, enables EIGRP on a router. ASN_NUMBER represents an autonomous system number and has to be the same on all routers running EIGRP, otherwise routers won’t become neighbors. The second command, network SUBNET, enables EIGRP on selected interfaces and specifies which networks will be advertised. By default, the network command takes a classful network number as the parameter.

To illustrate a configuration of EIGRP, we will use the following network:

eigrp sample topology

The network depicted above consists of only two routers. Each router has a directly connected subnet that needs to be advertised through EIGRP. The following figure show the EIGRP configuration on R1 and R2:

eigrp r1 configuration

eigrp r2 configuration

You can verify that routers have become neighbors by using the show ip eigrp neighbors command on either router:

show ip eigrp neighbors

The command above lists all EIGRP neighbors. The address field lists the neighboring router RID (router ID). The interface field shows on which local interface the neighbor relationship has been formed.

You can verify that routes are indeed being exchanged by using the show ip route command on both routers:

R1:

eigrp r1 show ip route

R2:

eigrp r2 show ip route

NOTE
The D character at the beginning of a line in a routing table indicates that the route has been learned via EIGRP.

Configuring EIGRP 2

By default, the network command uses a classful network as the parameter. All interfaces inside that classful network will participate in the EIGRP process.To enable EIGRP only on specific interfaces, a wildcard mask can be used. The syntax of the command is:

(router-eigrp) network WILDCARD_MASK

Consider the following example.

eigrp sample topology 2

Router R1 has two directly connected subnets, 10.0.0.0/24 and 10.0.1.0/24. We want to enable EIGRP only on the subnet connected to the interface Fa0/0. If we enter the network 10.0.0.0 command under the EIGRP configuration mode, both subnets will be included in EIGRP process because we’ve used a classful network number in the network command. To configure EIGRP only on interface Fa0/0, the network 10.0.0.0 0.0.0.255 command can be used. This will enable EIGRP only on interfaces starting with 10.0.0.X.

eigrp wildcard mask

By using the command show ip protocols, you can verify that only the network 10.0.0.0/24 is included in  EIGRP:

show ip protocols eigrp

upravnik