The concept of network classes is a little obsolete as subnets are now used to define smaller networks. These subnets may be part of a class A, B, C, etc network. For historical reference the network classes are defined as follows:
* Class A: Defined by the first 8 bits with a range of 0 - 127.
First number (8 bits) is defined by Internic i.e. 77.XXX.XXX.XXX
One class A network can define 16,777,214 hosts.
Range: 0.0.0.0 - 127.255.255.255
* Class B: Defined by the first 8 bits with a range from 128 - 191
First two numbers (16 bits) are defined by Internic i.e. 182.56.XXX.XXX
One class B network can define 65,534 hosts.
Range: 128.0.0.0 - 191.255.255.255
* Class C: Defined by the first 8 bits with a range from 192 - 223
First three numbers (24 bits) are defined by Internic i.e. 220.56.222.XXX
One class B network can define 254 hosts.
Range: 192.0.0.0 - 223.255.255.255
* Class D: Defined by the first 8 bits with a range from 224 - 239
This is reserved for multicast networks (RFC988)
Range: 224.0.0.0 - 239.255.255.255
* Class E: Defined by the first 8 bits with a range from 240 - 255
This is reserved for experimental use.
Range: 240.0.0.0 - 247.255.255.255