What is CIDR in Networking?

Classless Inter-Domain Routing (CIDR), also known as supernetting, is a revolutionary approach in network engineering for IP address allocation. Introduced in 1993, CIDR was developed to overcome the scalability issues associated with the class-based IP addressing system.

Evolution from Class-Based to Classless Networking

The previous system, based on IP classes (Class A, B, and C), was rigid and inefficient in addressing the growing needs of the internet. CIDR addressed these limitations by introducing a flexible and variable approach to IP address allocation. Unlike class-based systems, CIDR is not restricted to predefined subnetwork sizes, allowing for more efficient use of the IP address space.

How CIDR Works

CIDR is distinguished by its ability to organize IP addresses into subnetworks, regardless of their class. This flexibility enables the aggregation of multiple subnets into a larger network, or supernet. This aggregation is fundamental for efficient network routing, reducing the wasted address space and enhancing the capability of specifying network addresses in routers.

CIDR Notation in Virtual Private Clouds (VPC)

Classless IP addresses, a cornerstone of CIDR, are essential for creating Virtual Private Clouds (VPCs). These VPCs are isolated from other virtual networks, providing enhanced security and control. In the context of VPC creation, CIDR notation is used to specify a range of IPv4 addresses. This notation, typically expressed as a prefix and a number (e.g., /24), is pivotal in defining the size and range of the IP address block within the VPC.

Importance of CIDR in Networking

Understanding CIDR is crucial in modern networking. It’s not just a method for IP address allocation but a comprehensive system that impacts how networks are designed, deployed, and managed. Its role in efficient address utilization, improved routing, and network flexibility makes it a foundational concept in networking and internet architecture.