What does CIDR stand for?

CIDR stands for Classless Inter-Domain Routing. This method was introduced to improve the efficiency of IP address allocation and to address the limitations of the previous classful networking system.

In the traditional classful addressing scheme, IP addresses were divided into fixed classes (A, B, C), which led to significant wastage of IP addresses. As the internet grew, the demand for IP addresses increased, and the rigid structure of classful addressing became inadequate.

CIDR allows for variable-length subnet masking (VLSM), meaning that it enables the allocation of IP addresses in a more flexible manner. Instead of being restricted to specific block sizes, network administrators can aggregate multiple IP addresses into a single allocation or break down larger blocks into smaller ones as needed. This efficient use of address space helps reduce the size of routing tables and supports the scalability of the internet.

Understanding this concept is critical for networking professionals, as it has a direct impact on network design, IP address allocation, and the overall efficiency of routing protocols in an interconnected environment.