What does the term "subnet mask" define?

The term "subnet mask" defines the division of an IP address into network and host portions. It serves as a critical component in IP networking, allowing devices to identify which part of the address refers to the network itself and which part can be assigned to individual hosts (devices) on that network.

A subnet mask consists of a series of bits that correspond with the bits of the IP address. The bits in the mask set to '1' indicate the network portion, while the bits set to '0' represent the host portion. This division is essential because it enables routers and networking devices to route packets appropriately within and between networks, ensuring that data reaches the intended destination without confusion about the address structure.

Understanding how subnet masks operate is fundamental in configuring network devices, aiding in efficient IP address management, and preventing address conflicts within the same network.