CIDR Block

Classless Inter-Domain Routing is a method for allocating IP Addresses and routing. Its goal was to reduce the size of routing tables across the internet, and to slow down the exhaustion of IPv4 addresses. A CIDR Block specifies a subnet.

CIDR Block is based on variable-length subnet masking, which gives a finer control of the size of subnets.

CIDR Blocks are expressed with the “CIDR Notation”, which is an IP Address followed by a suffix indicating the number of bits that are part of the subnet. I.e.: 192.0.2.0/24 means that the first 24 out of the 32 bits of that IP Address are part of the subnet.