What is IP or Internet Protocol

Internet Protocol is an address of a computer on a network. An IP address is a 32 bit address. The IP addresses are unique i.e. no two computers, connected to the internet can have same IP addresses.

IP addresses when started used the concept of classes. This architecture is called class-full addressing. In the mid of 1990s, a new architecture was introduced and was called classless addressing and eventually superseded the original architecture. However, part of the Internet is still using class-full addressing, but the migration is very fast. In classless addressing variable-length blocks are assigned that belong to no class. In this architecture, the entire address space (232 or 4,294,967,296 addresses) is divided into blocks of different sizes. Class-full addressing is a special case of classless addressing.

In case of Class-full addressing, five classes of available IP ranges are there i.e.: Class A, Class B, Class C, Class D and Class E, while only A, B and C are commonly used, Class D and Class E are reserved for special purposes. Each class allows for a range of valid IP addresses.

Below is a listing of these addresses.


Address Range


Class A to

Supports 16 million hosts on each of 127 networks.

Class B to

Supports 65,000 hosts on each of 16,000 networks

Class C to

Supports 254 hosts on each of 2 million networks.

Class D to

Reserved for multicast groups.

Class E to

Reserved for future use, or Research and Development Purposes

NOTE: Ranges 127.x.x.x are reserved for loopback or local host and range broadcasts to all hosts on the local network.