Subnet masks (IPv4) and prefixes (IPv6) - IBM
www.ibm.com › docs › enOct 10, 2010 · Subnet masks (IPv4) and prefixes (IPv6) identify the range of IP addresses that make up a subnet, or group of IP addresses on the same network. For example, a subnet can be used to identify all the machines in a building, department, geographic location, or on the same local area network (LAN).