subnet mask

A number used to identify a subnetwork so that an IP address can be shared on a LAN.

An IP address has two components, the network address and the host address.

For example, consider the IP address Assuming this is part of a Class B network, the first two numbers (66.201) represent the Class B network address, and the second two numbers (69.207) identify a particular host on this network.

See also : dark fiber  
NetLingo Classification: Technical Terms