IP v4 utilizes a 32bit address which is assigned to hosts. An address is written as 4 octets separated by periods and may range from 0.0.0.0 through to 255.255.255.255. Each address consists of a network number, an optional subnetwork number and a host number. The network portion of the address is used for routing, and the host number is used to address an individual host within the network or subnetwork. Across the Internet, IPv4 addresses are organized using CIDR (Classless Inter Domain Routing).