|  | 10.7 | Creating a Subnet
| 10.7.8 | Private addresses

There are certain addresses in each class of IP address that are not assigned. These addresses are called private addresses. Private addresses might be used by hosts that use network address translation (NAT), or a proxy server, to connect to a public network; or by hosts that do not connect to the Internet at all.

Many applications require connectivity within only one network and do not need external connectivity. In large networks, TCP/IP is often used, even when network layer connectivity outside the network isn’t needed. Banks are good examples. They may use TCP/IP to connect to automatic teller machines (ATMs). These machines do no connect to the public network, so private addresses are ideal for them. Private addresses can also be used on a network where there are not enough public addresses available.

The private addresses can be used together with a network address translation (NAT) server. Either a NAT server or a proxy server to provide connectivity to all hosts in a network that has relatively few public addresses available. By agreement, any traffic with a destination address within one of the private address ranges will NOT be routed on the Internet.