CIDR stands for Classless Inter-Domain Routing and is a technical term used to describe the way Internet Protocol (IP) addresses are assigned to devices connected to a network. CIDR allows for variable length subnet masking (VLSM) to help create more efficient networks that have less wasted space. In other words, it allows networks to use a mix of subnet sizes within the same network.
In the early days of the internet, IP addresses were divided into two distinct classes: A and B. These classes generally followed certain structures that had built-in limitations, such as the size of the subnets and number of hosts within each. As the internet grew, these limitations became more apparent, leading to the development of variable-length subnet masks or VLSMs, and later CIDR.
It works by adding additional bits to the IP address and using them to create smaller subnets. This allows for more efficient routing of traffic and improved network performance, since resources can be allocated more precisely. For example, with CIDR an administrator can assign four IP addresses to one host, while previously they could only allocate a single address.
It also plays an important role in mitigating IP address exhaustion. It allows building blocks of IP addresses to be broken down into smaller segments, resulting in a more efficient use of IP address space. This is especially important in today’s world where IPv4 address space is limited and IPv6 is not yet widely adopted.
It is a crucial tool for network administrators and is used daily in LANs and WANs around the world. By allowing for more efficient use of IP address space, CIDR has helped ensure that networks remain reliable, secure, and operate at optimal speeds.
