Classful Addressing

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In this class, we will try to understand Classful Addressing.

We have already discussed the concepts of the Hierarchy of addressing.

Classful Addressing

The main objective of classful addressing is to utilize the IP address available efficiently. 

The IP addresses are grouped in classes based on the number of bits in the prefix.

There are five groups they are:

1. Class A
2. Class B
3. Class C
4. Class D
5. Class E

Class A

Class A addresses the prefix size is 8-bits, and the suffix size is 24 bits.

With 8-bits in the prefix and 0 as code, the number of networks possible is 2^7 = 128, and the number of possible IP addresses is around sixteen million.

The number of hosts in any network is 2^(Number of Suffix bits) – 2.

The image below shows how the class addresses are divided.

Class B

Class B addresses the prefix size is 16-bits, and the suffix size is 16 bits.

With 16-bits in the prefix and ’10’ as the code, the number of networks possible is 2^14 = 16,384, and the number of possible IP addresses in each ‘network’ is around sixty-five thousand.

The image below shows how the Class B addresses are divided.

Class C

Class C addresses the prefix size is 24-bits, and the suffix size is 16 bits.

With 24-bits and 110 as the code, the number of networks possible is 2^21 = 2,097,152, and the number of possible IP addresses in each ‘network’ is 256.

The image below shows how the Class C addresses are divided.

Class D and Class E

Class D and Class E addresses do not have prefix and suffix divisions.

Class D and Class E codes are 1110 and 1111, respectively.

The image below shows how the Class D and Class E addresses are divided.