Describe what a subnet mask does.

A subnet mask is a crucial component in networking that serves the primary function of identifying the network and host portions of an IP address. When a device connects to a network, it is assigned an IP address, which consists of a network part that signifies the specific network to which the device belongs, and a host part that identifies the device itself within that network.

The subnet mask works in tandem with the IP address by defining how many bits represent the network and how many bits represent the host. For instance, in a typical subnet mask like 255.255.255.0, the first three octets (255) indicate that the first 24 bits of the corresponding IP address belong to the network, while the last octet (0) indicates that the remaining 8 bits are available for host addresses.

This distinction is essential for routing data packets across networks, as routers need to understand which portion of the IP address pertains to the network to properly direct communication to the correct destination. The subnet mask thus plays a pivotal role in the organization and management of networks, ensuring efficient data transmission and connectivity between multiple devices.