What is IP in Networking?

• What is IP?
  At the 3^rd layer of OSI model so many routed protocols work like IP, IPX, AppleTalk. IP is the most common used routed protocol worked on Network Layer of OSI Model. IP is responsible to send the traffic  and to attach the IP header to the data before sending it to the Data Link Layer.
  
  
  
• What is IP or IPv4 Address?
  • This is the logical address of a device.
  • IP address is use to identify a device over the network.
  • Its of 32 bits or 4 Bytes in size.
    
    

There are two type of notation to identify an IP address. 1^st one is Binary Notation which is actually used by the machines. As we know our machines can only understand to bit values. So they will always use ip address as bit values.
    EX: 1010001000101111101011010101010

But if I am talking about the humans then its too hard to understand the binary notation easily for us. So in this case another notation is there. That’s known as The Dotted Decimal Notation or Format.
Ex: 192.168.1.1
In that for the ip address has been divided into 4 fields. Each filed having a size of 8 bits or 1 Byte. The fields of IP address are known as Octets. The vale in each field will in Decimal format. And as all field have a size of 8 bits. So that the value of a field can be from 0 to 255. Actually the value of 8 bit will be 256. But in networking as we are starting from 0 instead of starting from 1, so the value count till 255.

Class Of IP Address:

As per our communication types and looking at the organizational size the class the IP address has been divided into 5 Classes. Starting from A to E. Where the A.B & C classes are used for unicast communication. Class D used for multicast communication and Class E used for Research and development purpose. We can purchase IP networks from Class A,B & C for general communication purpose.

 
How to detect the class of a IP address?

 There are ways to detect the class of a ip address. The way to detect a class of ip address is deferent for human being and different for machines. Machine detect the class of an ip address by looking at 1^st few bits from the 1^st octet of the ip address value. And we human beings detect the class by looking at the 1^st octet decimal value. There are some ranges fixed for each class. Next you will get all information in each class section below.

• Class A:
  Used for unicast communication.
  The class A networks are basically used with big organizations.
  One Class A ip network can have a maximum user limit of up to 16777216 users.
  The 1^st bit of a class A ip is fixed with the value of 0. As we know the 1^st octet can have total 8 bits. So after fixing the 1^st bit as 0 we can get the value range as below.
  
  

ü    Binary value	ü    Decimal value
ü    00000000 Minimum Value	ü    0
ü    01111111 Maximum Value	ü    127

So the range of class A ip address will be from 0.0.0.0 to 127.255.255.255. But 0.0.0.0 network is reserved for some specific purpose like Default route & default address. So the Class A ip network can be range from 1.0.0.0 to 127.255.255.255. The network 127.0.0.0 is also reserved. And its use to check whether my TCP/IP stack is working or not.

The subnet mask of a class A address is fixed with 255.0.0.0. So the 1^st octet will always remain unchanged and the value of other 3 octets can changed. So here the 1^st 8 bits are known as network bits and the rest 24 bits are known as the host bits. In networking we can’t do change on the network bits, we can only do changes with the host bits.

• Class B:
  Used for unicast communication.
  The class B networks used in medium size organizations.
  A class B network can have maximum of 65536 users.
  The 1^st 2 bit of a class B address is fixed with binary value of 10. So the ranges will be:
  
  

ü    Binary Value	ü    Decimal Value
ü    Min – 10000000	ü    128
ü    Max – 10111111	ü    191

So the class B ip address is ranges from 128.0.0.0 to 191.255.255.255.
The network 169.254.0.0 is reserved for APIPA use.
The default subnet mask for a class B ip will be 255.255.0.0.
So the first 2 octets are fixed and are network bits and the rest two octets can be changed and are the host bits.

• Class C:
  Used for unicast communication.
  The class C ip networks are basically used in small organizations.
  A class C ip can have maximum up to 256 users.
  The 1^st 3 bits of class c ip is fixed with binary value 110. So the class C ip address range can be:
  
  

ü    Binary Value	ü    Decimal Value
ü    Min – 11000000	ü    192
ü    Max – 11011111	ü    223

So class c networks ranges from 192.0.0.0 to 223.0.0.0.
The default subnet mask of a class c ip address is 255.255.255.0. so the 1^st 3 octets are fixed as network bits and can’t be changed. We can only do changes on the 4^th octet.

• Class D:
  These ip address are used for Multicast Communication only.
  The 1^st 4 bits of a class D ip is reserved with binary value 1110. So the range of 1^st octet can be from 11100000 (224) to 11101111 (239).
  There is no subnet mask for these class IPs.
  
  
• Class E:
  These IP are used for research and development.
  The 1^st 4 bit fixed with binary value of 1111. So the ranges will be from 11110000 (240) to 11111111 (255).
  Here also no subnet used.