IP Addresses A host on an internetwork is identified by an IP address. This is a 32-bit number that uniquely identifies the host across the entire internetwork. This address is typically written as a set of 4 numbers (octets) separated by dots. Each number may be in the range of 0-255. Example: Certain IP address ranges are reserved to address a group of machines: Broadcast addresses (targeting all machines in a given sub-net), and Multicast addresses (targeting a group of machines that may be scattered across the entire internetwork).