What is a subnet mask?

A subnet mask is indeed a number used to divide an IP address into its network and host components. This division is crucial for routing traffic within a network. The subnet mask works by masking the IP address to indicate which part of the address is used to identify the network and which part is used to identify the specific device (host) within that network.

In practice, the subnet mask is expressed in a format similar to an IP address itself, with sets of numbers that define the size of the network. For example, in a subnet mask of 255.255.255.0, the first three octets (255) represent the network part, while the last octet (0) indicates the available addresses for devices within that network. Therefore, understanding subnet masks is fundamental for network configuration and management, as they enable efficient routing and traffic organization.

The other choices either describe unrelated concepts or functions that do not pertain to the definition of a subnet mask, such as hardware management, encryption methods, or wireless configuration setups.