subnet mask
compound.compound. a set of numbers used in computer networking to divide a large network into smaller, manageable parts. It helps your computer figure out which other devices are on its local network and which are outside.
compound. a 32-bit number used to mask an IP address and divide the IP address into network address and host address bits. It identifies which portion of an IP address refers to the subnet and which refers to the device itself.
You need to enter the correct subnet mask to connect to the network.
The IT technician configured the router with a subnet mask of 255.255.255.0 to ensure all office computers could communicate locally.
By applying a custom subnet mask, network administrators can efficiently allocate IP address space and reduce unnecessary broadcast traffic across the wider corporate infrastructure.
A compound term formed from the prefix sub-, meaning below or within, and the nouns network and mask. The usage follows the technical sense of a mask as a filter that selectively obscures or reveals specific data.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.
Typically appears as a four-part number separated by dots, similar to an IP address.
Last updated July 22, 2026