What Are Valid IP Addresses?

By Clifton Watson

IP addresses are used to identify computers on a network.
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Devices that connect to other devices or to the Internet over a network using standard Internet protocols each have an IP address. These addresses identify the devices. To make them easily read by humans, the IP addresses consist of binary numbers, typically in four numerical segments.

IP History

IP addresses as of 2011 are the fourth generation of IP addresses called IPv4. They were first described in 1981 and have been in use since 1983. The Internet Engineering Task Force, a loose affiliation of computer scientists and engineers who work together to come up with the standards that govern Internet communication, developed the IP address scheme. The IETF's overall goal is to enhance and simplify Internet communication; the IP system fits within the group's mission as a way to keep various Internet-enabled devices organized.

IP Assignments

The Internet Assigned Numbers Authority, or IANA, is the organization that assigns IP addresses. This is a global body that assigns IP addresses to various Internet Service Providers and users across the world. There are five main regions receiving IP address allocations covering the Internet user base worldwide. The Internet Corporation for Assigned Names and Numbers based in California, which itself operates under contract from the U.S. Department of Commerce, is the group that manages the IANA. Therefore, the IANA must comply with the standards and regulations set by the U.S. Department of Commerce.

IP Address Make-Up

Four groups of numbers make up an IPv4 address. A typical address might look something like this: The various numbers define the class and identity of the network device. A, B and C are the three main classes of networks consumers and professionals use. There are network classes D, E and F, but these are for special, experimental use and the public does not use them.

Valid IP Ranges

Class A IP addresses are networks through Class B is networks through Class C is through Class A networks are identified by the first number, while Class B networks use the first two numbers and Class C the first three. The remaining numbers in an IP address identify the specific device on the network. All of the numbers in an IP address use the 0-255 range, with the exception of the first number in Class C networks going up to 223. So is a valid IP address and denotes a Class B network (178.64) and a device identifier of 12.22. Any IP number that falls outside the ranges described here is not valid for general use.