The Internet Assigned Numbers Authority (IANA) has allocated three IP address ranges that are to be exclusively used for private Internet networks:

  • 10.0.0.0 – 10.255.255.255 (10/8 prefix)
  • 172.16.0.0 – 172.31.255.255 (172.16/12 prefix)
  • 192.168.0.0 – 192.168.255.255 (192.168/16 prefix)

The first block “10.0.0.0 – 10.255.255.255” is referred to as the 24-bit block, the second “172.16.0.0 – 172.31.255.255” as the 20-bit block, and the third and final block “192.168.0.0 – 192.168.255.255” is referred to as the 16-bit block.

192.168.0.0 – 192.168.255.255 is a set of 256 contiguous Class C network numbers. (IP addresses are classified into different classes based on the number of bytes that represent the network. A Class C IP address is one where the first three bytes represent the network. The total number of possible networks in Class C is 2,097,152).

The IP address 192.168.0.0 is the beginning of the Class C private range of IP addresses. Network routers most often use it to generically refer to the private network. It is unavailable for use as a static IP address, as it is reserved for use as a network address. Therefore, by convention, most routers use 192.168.0.1 as the default router address, as it is the next available IP address in this private IP range.