CIDR

Updated: 06/22/2024 by Computer Hope
classless inter-domain routing

Also known as supernetting, CIDR (Classless Inter-Domain Routing) is a system that allows one IP address to designate many unique IP addresses. CIDR was created to replace the Class A, B, and C network-based system to slow down the exhaustion of limited IPv4 addresses, and reduce the size of routing tables.

Tip

More information on CIDR is available in RFC 1518 and 1519.

CIDR IP example

A CIDR IP address is quite similar to a standard IP address in its appearance. The only difference is that the CIDR version ends in a forward slash followed by a number. For example:

201.107.4.24/13

That number, called the IP network prefix, designates how many addresses are covered by the CIDR. The number 13 in our example above indicates a capacity for 524,288 addresses.

Computer acronyms, IP address, IPv4, IPv6, Network terms, Subnet mask