Using Private IPv4 Addresses
The IANA has reserved three blocks of IPv4 addresses for companies to use on their private networks. These addresses are defined in RFC 1918, Address Allocation for Private Internets. You can use these private addresses, also known as 1918 addresses, for systems on local networks within a corporate intranet. However, private addresses are not valid on the Internet. Do not use them on systems that must communicate outside the local network.
The following table lists the private IPv4 address ranges and their corresponding netmasks.