Internet Protocol address (IP Address )

Ip address belongs to OSI  3rd  layer (network layer)  and it a logical address to identify a device on TCP/IP network .
we have two options for IP address

1. IPV4 (IP version 4)
2. IPV6 (IP  version 6)

           
The format of an IPV4 address is a 32-bit numeric address written as four part separated by periods. Each parts are called Octet (8Bit number system). IPV4 is divided into 4 classes .

0-255	0-255	0-255	0-255
First Octet	Second Octet	Third Octet	Fourth Octet

Based on the value of first octet we can understand the IP belongs to which class.

Class A	1.0.0.0 –  126.255.255.255
Class B	128.0.0.0- 191.255.255.255
Class C	192.0.0.0-223.255.255.255
Class D	224.0.0.0-239.255.255.255
Class E	240.0.0.0-255.255.255.255

  
An IP address can be static or dynamic. A static IP address will never change and it is a permanent Internet address. A dynamic IP address is a temporary address that is assigned from DHCP Server in the Network.

IANA-reserved private IPv4 network ranges

Class A	10.0.0-10.255.255.255
Class B	172.16.0.0.-172.31.255.255
Class C	192.168.0.0-192.168.255.255

Network identify by 1 and Host identified by 0.

Mask

Class A	255.0.0.0
Class B	255.255.0.0
Class C	255.255.255.0
Class D	Multicasting
Class E	Experimental

The MASK is used to describe how may networks and how many host per network  in IPV4 classes.
ie. In Class A - MASK =255.0.0.0 =11111111.00000000.00000000.00000000
Network Bit= 11111111=8Bit
Host Bit =00000000.00000000.00000000 = 24Bit

In Class A  total 2^8 Network and 2^24 Hosts.
In  Class B Network=2^16 and Host=2^16
In Class C Network=2^24 and Host=2^8