Classless Interdomain Routing (CIDR) is a method used in IP addressing to enhance the efficiency and scalability of routing on the internet. It is a technique that allows more flexible allocation of IP addresses, moving away from the older and more rigid class-based addressing system.
CIDR eliminates the concept of predefined class boundaries and introduces a more granular approach to IP address allocation. In the traditional class-based addressing system, IP addresses were divided into three classes (A, B, and C) with fixed ranges. However, this led to inefficient use of IP address space as organizations were often assigned more addresses than they actually needed.
With CIDR, IP addresses are allocated in variable-length prefixes, represented by the combination of an IP address and a slash (/) followed by a number. This number indicates the length of the prefix in bits, which determines the network portion of the address and the number of available host addresses. CIDR allows for the allocation of any number of IP addresses to networks of different sizes, resulting in more efficient use of the address space.
CIDR also simplifies routing by hierarchical aggregation. Instead of routing traffic to individual IP addresses or classes of addresses, CIDR allows routing tables to be summarized based on the common prefixes of IP addresses. This reduces the number of entries in routing tables and enables faster and more efficient routing decisions.
Overall, CIDR revolutionized IP addressing and routing on the internet by allowing for more flexibility and scalability, leading to optimal allocation and utilization of IP addresses and improving the efficiency of routing protocols.
