Explain Classless Inter-Domain Routing.

It is a new addressing scheme for the internet that permits for more efficient allocation of IP addresses than old class A, B and C addressing scheme. In place of being restricted to network identifier or prefixes of 8, 16, or 24 bits, CIDR at present uses prefixes wherever from 13 to 27 bits. Therefore, block of addresses can be allocated to a network as small as 32 hosts or to such with 500,000 hosts. It permits for address assignments which much more closely fit an organization's specific require.

A CIDR address contains the standard 32- bit address and also information on how many bits are utilized for the network prefix. For illustration in CIDR address 206.13.01.48/25, the /25 shows that the first 25 bits are used to recognize unique network leaving the remaining bits to identify the exact host.