Classes of IP addresses

TCP/IP defines five classes of IP addresses: class A, B, C, D, and E. Each class has a range of valid IP addresses. The value of the first octet determines the class. IP addresses from the first three classes (A, B and C) can be used for host addresses. The other two classes are used for other purposes (class D for multicast and class E for experimental purposes).

Classes of IP addresses:

 

Special IP address ranges:
0.0.0.0/8 – addresses used to communicate with the current network
127.0.0.0/8 – loopback addresses
169.254.0.0/16 – link-local addresses (APIPA)