Learn about IP addresses and their classes :

An IP address consists of four so-called octets separated by dots. An octet is a binary number of eight digits, which equals the decimal numbers from 0 to 255. To make IP addresses easier to read and write, they are often expressed as four decimal numbers each separated by a dot. This format is called "dotted-decimal notation".

In a LAN based on TCP/IP, an IP address must be assigned to each host (computer or device) in the network. The IP address must be unique to each host. (If two hosts were given the same address, the data to these hosts would be picked up randomly by one of them - be it the intended receiver or not - causing network irregularities).

Classes of IP Addresses :

In order to provide the flexibility required to support differently sized networks, IP addresses come in three classes - A, B, and C. Every class fixes the boundary between the network portion and the host portion of the IP address at a different point. This makes them appropriate for different size networks.

Class C addresses allow 254 hosts per network and are typically used by smaller and middle-sized companies. Class B networks a maximum of 16,384 hosts, while Class A networks allow more than 16 million hosts. As a consequence, Class A networks are only used by large organizations.