IP Address Classes and Special IP Address Ranges.

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: - addresses used to communicate with the current network - loopback addresses - link-local addresses (APIPA)