Subnet is a segment on the internet of an Internet-connected local area network (LAN) that is differentiated from other segments by using an operation (called a mask) that is performed on the network’s IP address. Subnets share a common IP address with the rest of the network of which they are apart, but they can function autonomously. Subnet is a virtual unit identified conceptually by using the addressing methodology, and it is generally created to reflect valid organizational distinctions, even if the members of an organizational unit are using two or more physically dissimilar portions of the network. See IP address, LAN.