Advertising EIGRP for router interface

[Horacio Gutierrez]

Hello,

Why is it that between routers if you are using eigrp you have to advertise the routers interfaces in eigrp that connect to each other not only the networks behind the router?

[John Blakley]

You're not really advertising the router interfaces that connect to each other. You're enabling eigrp on those interfaces. When you use the network command, the router will match that network to the interface on the router in order to start sending hellos out of that particular interface. If it receives a hello from another router with the same AS number and network, it will try to form a neighborship between routers. Without using the network command, eigrp doesn't know what interface you want to use to create a neighborship.

HTH,

John