/31 subnet

showint

/32 is used, for example, to define loopback.
/30 is used in p2p connections.

But in which cases is used /31 subnet? There can't be any host, just network address and broadcast.

networker050184

You use it on a p2p link. There are two addresses in a /31, one fore each side of the link. Do you really need a network or broadcast when there are two hosts? Most vendors support /31s usage on even ethernet links now.