Servers are capable of using multiple IP addresses. Mac Pro and Xserve computers have two network interfaces installed. Apple also sells network interfaces, as do a number of third-party entities. Additionally, each interface can run multiple IP addresses, providing a practically infinite number of options for interfaces and addresses.

Using multiple IP addresses on a single port is known as multihoming. In order to configure a single interface to have two IP addresses, use the plus sign (“+”) to bring up the “Select the interface and enter a name for the new service” screen. Here, select the network interface you would like to configure a second IP for and provide a name for the second instance of the interface (Figure 1-7).

Figure 1-7. Configuring multiple hardware ports

Click on Create and the second port will be listed in the Network System Preference pane. The port can then be configured as any other port would be.