All About IP Address

What is an IP address ? If you know the answer of this question then networking will be very easy for you.Here i am giving a detailed tutorial on this topic.This tutorial is meant for begineers.Advanced user can refresh their knowledge.


The IP address is a 32-bit number that is unique to your computer. No two systems can have the same IP address. An IP address is similar to the address of your home, which is the method by which other people send mail to you. An IP address works the same way on a TCP/IP network — you will assign the number to your computer, and it is the method other computers use to send information to your computer.


An IP address is made up of four sets of numbers separated by periods. This is called the dotted decimal notation format of the IP address. An example of an IP address in the dotted decimal notation format is

Code:

198.70.26.200

Each of the four sets of numbers is referred to as an octet (because each octet represents 8 bits of data).

The IP address is made up of a network ID and a host ID:

The network ID is a unique number used only by your network and is the same for all computers on the same network.
For example, in the IP address

Code:

198.70.26.200

the first three octets

Code:

198.70.26

make up the network ID.

The host ID portion uniquely identifies a computer on the network.
For example, in the IP address

Code:

198.70.26.200

the last octet

Code:

200

make up the host ID. Only one computer on the

Code:

131.107.26.y

network can have the host ID of

Code:

200

There are three major classes of IP addresses: Class A, Class B, and Class C. The different IP address classes support a different total number of workstations on the network. For example, a Class A network (a network using Class A addresses) supports up to 16,777,214 network devices, while a Class B network supports 65,534 network devices, and a Class C network supports only 254 network devices.

Class A

1. Number of Hosts: - 16,777,214
   First Octet Value:- 1–126
   Octet Summary:- n.h.h.h

Class B

1. Number of Hosts: - 65,534
   First Octet Value:- 128–191
   Octet Summary:- n.n.h.h

Class C

1. Number of Hosts: - 254
   First Octet Value:- 192–223
   Octet Summary:- n.n.n.h

Their are also other classes of IP address Class D, Class E but they will be discussed later,may be in some other thread.An IP address class is determined by seeing the value of its first octet.
Any address starting with 127 is illegal because this address is reserved for the loopback address.

Here’s an IP address example: Computer A has an IP address of

Code:

222.22.220.22

and it initiates communication with Computer B, whose IP address is

Code:

222.22.221.23

Are the two workstations on the same network? Looking at the first octet, you can see that the number

Code:

222

is a Class C address, which means that the first three octets make up the network ID, and the last octet is the host ID. Since there is a difference in the first three octets (which is the network ID), these two computers are on different networks.

Another way to tell whether your computer is on the same network as the computer you are trying to communicate with is to look at the subnet mask. The subnet mask is what your computer uses to determine whether the network device it is trying to communicate with is on the same network or not.

If there is a

Code:

255

in the subnet mask, then the corresponding octet in the IP address is part of the network ID. Once the network ID is known, any systems that have the same network ID are considered to be on the same network — otherwise they would have a different network ID.

For example:
IP Address

Code:

145.90.87.213

belongs to Class B and first two octet makes the network id i.e

Code:

145.90

and its subnet mask will be given by

Code:

255.255.0.0

Computers firstly checks the subnet mask of other computers and then compares the octets to start communication.

So this was a little explanation of IP Addressing. Hope you liked it.