EIGRP and wildcard masks

The network command in EIGRP uses a classful network as the parameter by default, which means that all interfaces inside the classful network will participate in the EIGRP process. We can enable EIGRP only for specific networks using wildcard masks. The syntax of the command is:

(router-eigrp)#network IP_ADDRESS WILDCARD_MASK

Consider the following example:

wildcard mask topology

In the picture above you can see a network with three hosts and a router. The router is directly connected to three subnets. Let’s say that we want to advertise only the subnet in EIGRP. We can use the wildcard mask of to do this:

network command wildcard mask

Using the show ip protocols command, we can verify that the network is included in EIGRP:

show ip protocols command

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