What is the purpose of a subnet mask?

The purpose of a subnet mask is to distinguish the network and host parts of an IP address. An IP address consists of two main components: the network portion, which identifies the specific network the device belongs to, and the host portion, which identifies the individual device within that network. The subnet mask provides a way to separate these two components by using a series of bits that indicate how many bits are used for the network address versus how many bits are used for the host address.

For instance, in a typical subnet mask like 255.255.255.0, the first three octets indicate the network part, while the last octet is reserved for the hosts. This allows devices on the same network to communicate with each other while also facilitating routing to external networks. Understanding this aspect of subnet masks is essential in network design and management, as it influences how many devices can be accommodated in a given network.