Private Networks

Many things bring privacy to a network. There the firewalls that bring a little bit of privacy, but usually people who have a private network set it up so that they have their own range of IP addresses. There are a few IP address ranges that are reserved for private use by the Internet Assigned Numbers Authority (IANA) (See RFC 1918). Here is a chart:

Address/Netmask	Comments
10.0.0.0/8	Free to use. (Old DARPA Range)
172.16.0.0/12	Free to use.
192.168.0.0/16	Free to use.

You can pick any of these ranges and use any of the addresses here as long as the addresses do not go out onto the Internet. The way that you can prevent their entering the Internet is to translate the addresses.