original addresses were assigned by class, classes A,B,C,D and E. Depending on how much address space you needed you would be assigned a certain class of address, now though this classful addressing is no longer used as it has proved to be far too wasteful since the growth of the internet and ever growing demand for IP addresses, VLSM is now used to reduce the amount of wasted address space. It is still important to know about the classful address system though as subnetting using VLSM requires prior knowledge of the classful address ranges in order to correctly subnet the network.


Address Range


Class A to

Supports 16 million hosts on each of 127 networks.

Class B to

Supports 65,000 hosts on each of 16,000 networks.

Class C to

Supports 254 hosts on each of 2 million networks.

Class D to

Reserved for multicast groups.

Class E to

Reserved for future use, or Research and Development Purposes