IP Reserved, Private, and Loopback Addresses
In addition to the unusable numbers with special meanings just discussed, several other sets of IP addresses have special uses, and are therefore not available for normal address assignment. These generally fall into three categories: reserved, private, and loopback addresses.
Several blocks of addresses were designated as reserved with no specific indication given as to what they were reserved for. Perhaps they were set aside for future experimentation or for internal use in managing the Internet. (In general, it's a good idea to set aside some portion of any limited resource for unanticipated needs.)
A couple of these blocks appear in each of the three main classes (A, B, and C), at ...