Subnet A subnet is a segment of a network. Subnetting allows a network administrator to divide one physical network into smaller logical networks, thereby controlling the flow of traffic for security or efficiency reasons. Subnets are created by using a so-called subnetmask as a deciphering key to divide a network into smaller pieces. The subnetmask is used by routers and network devices to determine where traffic should be routed to. Subnets can again be subnetted into sub-subnets. The typical subnetmask for a network with up to 254 hosts is 255.255.255.0. The calculation of correct subnet masks require deeper knowledge of the binary system, and is only necessary when dealing with network administrative tasks, such as setting up several logical networks on one physical network.
