What is the purpose of a network mask?

While a network mask helps determine the number of hosts, it is not used in conjunction with a wildcard mask for this specific purpose; wildcard masks are primarily used in Access Control Lists (ACLs).

The primary purpose of a network mask is to logically divide an IP address into two distinct components: the network portion (prefix) and the host portion, allowing devices to determine if a destination is on the local network or requires routing.

The network mask itself does not hide subnets; Network Address Translation (NAT) is the mechanism used to translate private IP addresses to public ones, thereby obscuring internal network structure from external networks.

While network masks are integral to both classful and classless networking, their purpose is not to differentiate between these historical classifications, but rather to define network and host bits regardless of class.