Question

What do think CIDR was needed so soon (ten years is not a lot of time ) after classful addressing was implemented ?

Answer 1

Class A supports 2²⁴ addresses = 16777216 addresses.

Class B supports 2¹⁶ addresses = 65536 addresses.

Class C supports 2⁸ addresses = 256 addresses.

But if an organization needs 260 addresses, then he must go to class B and there are a lot of wastage of the IP addresses. This problem was resolve by CIDR.

CIDR:

CIDR stands for Classless Inter-Domain Routing, replace the previous system of allocating the IP address that was based on classes like class A, class B, etc. and CIDR is based on variable-length subnet masking.

An IP address is an identifier or label used to identify a machine on the internet or a particular network. Each of the devices on the internet must have an IP address for identification.

For example:

Let us suppose the given IP address is:

193.62.83.0/25

The netmask in binary representation will be:

11111111 11111111 11111110 00000000

The netmask in decimal representation will be:

255 255 254 0

Here, 25 bits are used for network id, and the last 8 bits are used for host id.

Total number of IP addresses will be = 2⁹ = 512

In a network, the first and last IP addresses are used for the special purpose and the remaining addresses are used as a host address.

The total number of the host in this network will be = 512 - 2 = 510