CIDR is an effective method of IP Address# allocation especially for IPv4 Address developed by Internet Engineering Task Force (IETF) which utilises the prefix or the subnet mask. There is no default subnet mask for a network, instead it relies on Variable-Length Subnet Masking (VLSM)#. That being said, for CIDR to be deployed, the network must be contiguous, that is having the same network mask (the prefix must be larger than the default mask).
By using CIDR, we could reduce the size of the Routing Table as the supernet (network that is at a higher hierarchy) is able to summarise multiple network addresses with a subnet mask that is less than the classful subnet mask. Classless Routing Protocols# will be used for routing update.