How NAT Works

The following figure illustrates how NAT works.

Figure D–1 Simple NAT Network Conceptual Diagram

The private subnet 10.1.1.0 has one machine called Machine 1 that runs behind NAT 1, which uses 129.146.63.100, a translated IP address, for all communication from Machine 1 to hosts outside NAT 1. Communication from hosts outside NAT 1 to Machine 1 (129.146.63.100) are redirected to Machine 1 (10.1.1.1) by NAT 1.

A second private subnet (100.1.1.1) has one machine Machine 3 (100.1.1.1) and runs behind NAT 2, which uses 129.146.63.101 (a translated IP) for communication from Machine 3 to hosts outside NAT 2. Communication from hosts outside NAT 2 to Machine 3 (129.146.63.101) is redirected to 100.1.1.1 by NAT 2.