Subnetting

IPv4 Address Assignment

The IANA (Internet Assigned Numbers Authority) assigns IPv4 addresses/networks to companies based on their size.

For example, a very large company might receive a class A or class B network, while a small company might receive a class C network.

However, this led to many wasted IP addresses.

CIDR

When the Internet was first created, the creators did not predict that the Internet would become as large as it is today.

The IETF (Internet Engineering Task Force) introduced CIDR in 1993 to replace the 'classful' addressing system.

Classless Inter-Domain Routing

With CIDR, the requirements of:

• Class A = /8

• Class B = /16

• Class C = /24

... were removed.

This allowed larger networks to be split into smaller networks, allowing greater efficiency.

These smaller networks are called 'subnetworks' or 'subnets'.