Efficient IP Addressing and Network Management.
CIDR, or Classless Inter-Domain RoutingA method for allocating IP addresses and routing Internet Protocol packets. It was introduced in 1993 to replace the previous classful network addressing architecture., is a method for allocating IP addresses and routing Internet Protocol packets. It was introduced in 1993 to replace the original classful network addressing system (Class A, B, C) which was inefficient and led to rapid IPv4 address exhaustion.
At its core, CIDR allows for more flexible and efficient use of IP addresses by enabling variable-length subnet masking (VLSM) and route aggregation. This means network administrators can create subnets of varying sizes, perfectly matching the needs of their networks, rather than being restricted to fixed class sizes.
A CIDR block is represented as an IP address followed by a slash and a decimal number, like 192.168.1.0/24
. This notation combines two crucial pieces of information:
192.168.1.0
). It can represent a network address or a host address within that network./24
) indicates how many bits of the IP address are used for the network portion. This is also known as the subnet mask.The prefix length determines the boundary between the network and host parts of an IP address.
CIDR brought significant improvements to IP addressing and routing:
Multiple specific routes can be summarized into a single, more general route.
Enter an IP address and a prefix length to see the network details and how the bits are divided.