<u>Classless Inter-Domain Routing </u>gets its name from the notion that it ignores the traditional A, B, and C class designations for IP addresses and can therefore set the network-host ID boundary wherever it wants to, in a way that simplifies routing across the resulting IP address spaces.
Explanation:
CIDR refers to the Classless Inter-Domain Routing
It is a type of an IP addressing scheme that improves the allocation of IP addresses. It it ignores the traditional A, B, and C class designations for IP addresses and can therefore set the network-host ID boundary wherever it wants to, in a way that simplifies routing across the resulting IP address spaces.
The problem with the old method of IP routing was that an error would occurred whenever an organization required more than 254 host machines and hence it would no longer fall into class C category but it will fall in class B category . which meant that the organization needs to use a class B license even if they have less than 65,535 hosts. thus if an organization requires only 2,500 hosts, they end up wasting 63,000 hosts by holding a class B license which further decrease the availability of IPv4 addresses .