I understand that for classful networks in EIGRP we do not need a subnet mask. Why is this? When I do a show ip protocols the routes appear without a subnet mask which looks somewhat odd.

If I have a 192.168.0.0/16 network and just introduce the network into the EIGRP routing protocol as 192.168.0.0, how will EIGRP know that it is 192.168.0.0/16 and not say 192.168.0.0/24?

Or does EIGRP understand the network address from the host addresses assigned to the router's DC interfaces?

Thanks.