CIDR notation

Date: 2025 07-July 29

What is CIDR? - CIDR Blocks and Notation Explained - AWS

## What is CIDR?

Classless Inter-Domain Routing (CIDR) is an IP address allocation method that improves data routing efficiency on the internet. Every machine, server, and end-user device that connects to the internet has a unique number, called an IP address, associated with it. Devices find and communicate with one another by using these IP addresses. Organizations use CIDR to allocate IP addresses flexibly and efficiently in their networks.