An IP address  i s a unique identifier for the nodes in the network. It is like an entity for every terminal or node that is connected to the network.

It is a combination of 32 bit in which 4 decimal values , each one representing the 8 bits , in the range of 0 to 255 which are separated by the decimal points. It is also called as the dotted decimal notation.

Example: 140.179.220.200

Every IP address mainly consists of the two parts one is for the network and the other one is for the node.

The  class that the address belongs and the subnet mask will used to determine that which part is associated with the network address and which part is with the node address.

Each IP address is consisted of mainly two parts

Address Classes

There are 5 different address classes. You can determine which class any IP address is in by examining the first 4 bits of the IP address.

Class A addresses begin with 0xxx, or 1 to 126 decimal.

Class B addresses begin with 10xx, or 128 to 191 decimal.

Class C addresses begin with 110x, or 192 to 223 decimal.

Class D addresses begin with 1110, or 224 to 239 decimal.

Class E addresses begin with 1111, or 240 to 254 decimal.

Addresses beginning with 127 decimal, are reserved for loopback and for internal testing on a local machine.

[You can test this: you should always be able to ping 127.0.0.1, which points to yourself] Class D addresses are reserved for multicasting. Class E addresses are reserved for future use. They should not be used for host addresses.

Now we can see how the Class determines, by default, which part of the IP address belongs to the network (N) and which part belongs to the node (n).

Class A -- NNNNNNNN.nnnnnnnn.nnnnnnn.nnnnnnn

Class B -- NNNNNNNN.NNNNNNNN.nnnnnnnn.nnnnnnnn

Class C -- NNNNNNNN.NNNNNNNN.NNNNNNNN.nnnnnnnn