As mentioned earlier in this chapter, one of the least useful services in Lion Server is the Network Address Translation (NAT) service. Most Internet service providers (ISPs) supply you with one IP address. This address can then be used to put potentially thousands of computers on the same network using NAT, which then allows you to configure incoming connections to point at the server. These options are available in the Sharing System Preference pane on Lion computers until Lion Server is installed.
Once Server has been installed, use the Server Admin tool (available in /Applications/Server) to enable the service. To get started, open Server Admin and click on the name of the server in the SERVERS sidebar. Click on the Services tab and then check the box for NAT, clicking Save to show the NAT service under the server’s name in the Server Admin sidebar.
Click on the NAT service and then click on Settings in the NAT toolbar. Here, you will see options to configure the NAT service. These include:
Creates a gateway without NAT (where the server is used to route traffic and all servers use public IP addresses); this is very rare and in the event that you are using this option, think very carefully about whether you should be
Creates a gateway with NAT enabled; this option creates the traditional NAT connection used in practically every consumer-class router by default