# Network mask

A network mask is a mask that gets applied to an IP address . These are normally of the form 0.0.0.0 (empty mask), 255.0.0.0 (use the first 8 bits of the address), 255.255.0.0 (first 16 bits ), 255.255.255.0 (first 24 bits ), or 255.255.255.255 to use the whole address.