An Internet Protocol (IP) address is a 32-bit numerical label for uniquely identifying a host device on the [[Internet]]. The first three octets are the network address and the last octet is the host address. IPv4 is the current protocol, but coming is IPv6 which uses 128-bit addresses to support more addresses. The subnet mask is used by the TCP/IP to determine whether a host is on the local subnet or on a remote network. A subnet mask can be specified using Classless Inter-Domain Routing (CIDR) prefix.