Network and IP Address Basics

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Network Basics:

Introduction:

For example you want to connect to www.google.com. So request starts from your network and reaches destination network where it should reach destination host and then destination process.
Three steps:

  •   Destination Network 
  •   Destination Host
  •   Destination Service

So this domain name ‘www.google.com’ has to be converted to some numbers which a computer can understand. This is called IP address.

IP Address = Network ID + Host ID

How to convert domain name to IP Address?

Your ISP (Internet service provider) should provide with a Domain name service. Inside your network there should be a DNS server.
Domain name to IP address conversion is an overhead. So it is done only first time.

IP Addresses

Binary number system – base is 2 – number of symbols – 0 and 1

Remember: 21  to 210  thoroughly. 

20
21
22
23
24
25
26
27
28
29
210
1
2
4
8
16
32
64
128
256
512
1024


IP address consists of 32 bits divided into four parts of 8 bits each which is known as 4 octets


 
If one bit chosen we get two parts of 231 each.


Then if we choose one part out of it and again choose one bit we get two parts of 230 each and so on.
 

 



Let’s go in each class in detail:

Class A (Range 0-127)

Class A starts with 0 in binary

Number of IP addresses: 231

 
Out of 8 bit one bit is already fixed as 0 .

27  = 128 networks

226 = 16 million IP Addresses per network.

It can range from: 
 
0 0000000  -  0
0 1111111   - 127

0 and 127 are reserved and cannot be used

Generally Class A bought by very huge companies like NASA      
        
Class B (Range 128-191)

Class B starts with 10 in binary
Number of IP addresses: 230

 
Out of 16 bits for network id first two bits fixed as 10

214  = 16 k networks

216 = 64 k IP Addresses per network.

It can range from: 

10 000000 = 128 

10 111111 = 191

Generally Class B used by Banks. 

Class C (Range 192-223)

Class C starts with 110 in binary

Number of IP addresses: 229
 
Out of 24 network bits first three bits fixed as 110

221  = 2 million networks

28 = IP Addresses per network.

It can range from: 

110 00000 = 192
110 11111  = 225 

Generally small organizations use this class