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What are the classifications of classful IP addresses?
IP addresses are generally represented by a 32-bit unsigned binary value. It is represented in a dotted decimal format. For example, 9.250.7.5 is a valid IP address.
The IP address consists of a pair of numbers −
IP address = <network number><host number>
Class-based IP addresses
The first bits of the IP address specify how the rest of the address should be separated into its network and host part. This IP address consists of network ID and Host ID.
Classes of IP address
There are 5 classes of IP address in computer network, which are as follows −
- Class A
- Class B
- Class C
- Class D
- Class E
The numbers of IP addresses possible in a network of classes are as follows −
- Class A= 231
- Class B= 230
- Class C= 229
- Class D= 228
The representation of IP address = Binary notation, Dotted decimal notation( 4 octets).
The binary format of the IP address is: 10000000 00000010 00000111 00001001
The dotted decimal format: 192.169.175.8
{each octet is 8-bit representation total 32 bit representation of IP address}
Generally,
- Class A= start with ‘0’
- Class B= start with ‘10’
- Class C= start with ‘110’
- Class D= start with ‘1110’
- Class E= start with ‘1111’
Now let’s try to understand each class in detail −
Class A
The number of possible networks of class A= 27 =128
Size of each network = 224 = 16M.
Number of Hosts = (224 -2)
| 0 | 8 bits | 24 bits |
In Class A, we don’t use the starting address for all 0’s and the last address for all 1’s.
Therefore, practically number of network’s in Class A= 128-2 = 126
Range= 0-126
That is, Class A addresses use 7 bits for the <network> and 24 bits for the <host> portion of the IP address.
This allows for 27 -2 (126), networks each with 224-2 (16777214) hosts – a total of more than 2 billion addresses.
Class B
The number of IP Addresses= 230
Number of networks for class B= 214 =16K
Size of each network = 216
Number of Hosts= 216-2
<------------230---------------🡪
| 10 |
16 bits 16 bits
Starts with 10- - - - - - - - 10 0 0 0 0 0 0 =128 10 0 0 0 0 0 1 = . . 10 1 1 1 1 1 1 = 191
Therefore, Range= 128-191
That is, the Class B addresses use 14 bits for the <network> and 16 bits for the <host> portion of the IP address. This allows for 214-2 (16382) networks each with 216-2 (65534) hosts – a total of more than 1 billion addresses.
Class C
Number of IP Addresses= 229
Number of networks of Class C = 221 networks= 2 million
Size of each network= 28 IP addresses are in one network of Class C.
<------------229---------------🡪
| 110 |
21 bits 8 bits
Starts with 1 1 0- - - - - - - - 1 1 0 0 0 0 0 0 =192 1 1 0 0 0 0 0 1 = 193 . . 1 1 0 1 1 1 1 1 = 223 => number of Hosts
Therefore, range= 192-223
That is, Class C addresses use 21 bits for the <network> and 8 bits for the <host> portion of the IP address. That allows for 221-2 (2097150) networks each with 28 -2 (254) hosts – total of more than half a billion addresses.
Class D
Class D addresses are reserved for multicasting (a sort of broadcasting, but in a limited area, and only to hosts using the same Class D address). There is nothing Called as network ID and Host ID in Class D.
Class D starts with ‘1110…’ 1 1 1 0 0 0 0 0 =224 . . . 1 1 1 0 1 1 1 1 = 239
Therefore, Range= 224-239
This class is used for Multicasting and group emailing and group based broadcasting.
Class E
These addresses are reserved for future or experimental use.
There is nothing called network ID and Host ID in Class E.
Class E starts with ‘1111…….’1 1 1 1 0 0 0 0=240
.
. . 1 1 1 1 1 1 1 1 = 255
Therefore, Range= 240-255
It is used for Military applications.
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