There are three "classes" of IPv4 subnets. Essentially, these refer to which "octet" is set. Class A: A /8 network (netmask 255.0.0.0) - the first octet is set and the rest belong to you. i.e....
The IPv4 address space can be subdivided into 5 classes - Class A, B, C, D and E. Each class consists of a contiguous subset of the overall IPv4 address range.
There are 5 defined Classes for IP Addresses: Class A: 0.0.0.0 - 127.255.255.255Class B: 128.0.0.0 - 191.255.255.255Class C: 192.0.0.0 - 223.255.255.255Class D: 224.0.0.0 - 239.255.255.255Class E:...