IP Addresses & Categories

IP address is the logical address to identify the device in network.

IP address are of two types

1. IPv4
2. IPv6

In IPv4 32bits are divided into four octates. Each octate is separed with dot(.) and its known as dotted decimal notation. Total 4.3 billion IP address are again divided into 5 classes i.e., is from Class A,B,C,D,E based on priority bits. Priority bits are most significant bits from most significant octates.

Class	First octet range	Priority bit	Octet format	Usage
A	0-127	0	N.H.H.H	Large Networks
B	128-191	10	N.N.H.H	Medium Networks
C	192-223	110	N.N.N.H	Small Networks
D	224-239	1110	-	Reserved for multicasting
E	240-255	1111	-	Resrved for research and development

To calculate
Number of networks=2^N-P
where N=number of network bits and P=number of priority bits

Number of Hosts=2^H-2
where H=number of host bits

Network ID: Network ID is used for representing the network. It represents group of IP addresses. By default network ID contains 0 in the host portion.
First IP of the network is the network ID. ex: 192.168.1.0

Broadcast ID: Broadcast ID is used for broadcasting the information to other IP addresses which is belongs to same network. By default broadcast contains 255 in the host portion.
Last IP address of the network is broadcast ID. ex: 192.168.1.255

Valid IP address: Valid IP addresses exit between network ID and broadcast ID
Ex:192.168.1.2

Public IP addresses: Public IP addresses are the valid IP addresses which are routable over the internet. These IP addresses are not free of cost. Inorder to access them we have to purchase from Internet Service Providers(ISP).

Private IP addresses: Certain addresses from each class of the IP address are reserved for private networks. These addresses are called private IP address. These private IP addresses are not valid over the internet.

Private IP address from each class

Class A	10.0.0.0 - 10.255.255.255
Class B	172.16.0.0 - 172.31.255.255
Class C	192.168.0.0 - 192.168.255.255

Exclusion Range of IP address

• 0.0.0.0 is completely excluded from IP address range. it is called global ip.
• 
  127.x.x.x range of IP addresses are also excluded. It is called loopback addresses. It is used to check the compatability of Network Interface Card(NIC) with operating system as well as functionality of TCP/IP.
• 255.255.255.255 is also excluded. It is called broadcast ID.

NOTE:
169.254.0.0 - 169.254.255.255 Special range ip address used for dynamic purposes when we are using Dynamic Host Control Protocol(DHCP) to assign ip addresses. If no ip addresses available or any network problem raises this special range ip addresses are asigned by DHCP server.