27. Set Your Network Device Preference Order  SEE ALSO 30 Configure Networking Manually 43 Create and Configure a Location
Mac OS X allows you to configure multiple different networking devices, such as modems, Ethernet connections, and AirPort cards, and to place them in the order of your preference. With this arrangement, if the primary device is not plugged in or available, Mac OS X tries the next most preferred device. For instance, you might have an iBook with an AirPort card, an Ethernet cable you sometimes plug into, and a phone line. However, you don't always have the Ethernet cable plugged in, and the AirPort signal might sometimes be unavailable as well. You want to be able to set up Ethernet as your most preferred connection method, but if you don't have Ethernet plugged into your iBook, you want the computer to use AirPort instead. As a last resort, if neither of the other methods are available, you want to be able to use the modem and phone line to dial up. Mac OS X makes this configuration easy to set up.  KEY TERMS AirPort Apple's brand of wireless Internet connectivity devices. Operating over the industry-standard 802.11 protocol (also called Wi-Fi), AirPort and its faster successor AirPort Extreme allow you to connect to the Internet without wires, as long as a base station (a device connected physically to the Internet, which broadcasts the 802.11 signal that allows computers within range to access the network) is within range. Ethernet A physical connection to a LAN is done using Ethernet, a low-level communication protocol that involves cables that end in RJ-45 jacks, which resemble large phone jacks . All modern Macs have an Ethernet port, which runs at 10, 100, or (on top-end models) 1000 megabits per second.
27. Set Your Network Device Preference Order 
| 1. | Open Network Preferences
Open the System Preferences from the Apple menu; click the Network icon to open the Network Preferences pane.
| | 2. | Edit the Network Port Configurations From the Show drop-down menu, which contains entries for each of the network devices in your computer (which you can select to configure those devices directly, as you will see in 30 Configure Networking Manually ), select Network Port Configurations . A screen appears that contains an editable list of network devices. Each one of these devices is actually a port configuration , a combination of a network device (port) and a TCP/IP configuration. This allows you to define more than one configuration for a single portone set of TCP/IP settings for home, and another set for work, but both assigned to your Ethernet port. NOTE Every physical network has a different series of settings that you must apply in order to connect your computer to it. Your network at the office, for instance, might provide an Ethernet connection and broadcast its settings to your computer automatically, whereas at home, you might have to configure your TCP/IP settings manually, using a fixed address assigned by your service provider, in order to connect to a DSL modem. Locations allow you to save these configurations and switch back and forth between them with a single command. | | 3. | Drag Devices into Preferred Order To set up your iBook as described earlier, click and drag the port configurations into the following order: This organization means that your iBook will first try to connect to the network over the Ethernet connection, using the TCP/IP settings you have defined for it. If your Ethernet cable isn't plugged in, the iBook skips that configuration and tries to connect using the wireless AirPort connection. If AirPort isn't available (for instance, if you're out of range of the base station), the computer will fall back to the internal modem dial-up, although even that connection won't be available unless you manually tell the computer to dial the modem. TIP If you're using a less-preferred connection method (for instance, AirPort) and a more-preferred one becomes available (for instance, if you plug in the Ethernet cable), Mac OS X will automatically switch to the Ethernet connection. | | 4. | Enable and Disable Devices
Your Mac might have network devices you know you'll never use. For instance, you might have a computer without an AirPort card, so you know the AirPort configuration will never be used. You can remove it entirely from the preference list, saving time when your computer tries to connect to the Internet. To remove a device, deselect its On check box in the configuration list. Turning off a port configuration removes that configuration from the Show menu.
| | 5. | Create a New Port Configuration Suppose that you have two different sets of Ethernet settingsone for your home network and another one for your office. Depending on whether you're at home or at work, you want to be able to swap one set of TCP/IP settings for the other, with as little effort as possible. NOTE The TCP/IP settings that allow each of your network devices to connect to the Internet can be obtained from whoever provides your Internet connectivity service. At work or on campus, this would be the network administrator. At home, consult your Internet service provider to find out what settings you need for your Ethernet (or other) connection. Click the New button. A sheet appears that lets you define what kind of port configuration you want to create. Specify a name for the configuration and select the network device you want to use. You can select from the modem, Ethernet, or FireWire ports. If you want to make a copy of an existing configuration and make changes to the copy, select the configuration and click Duplicate . The Duplicate option isn't available for the AirPort device. After the new configuration has been created, you can then select it by name from the Show menu and apply the appropriate TCP/IP settings that allow it to connect to the network. See 29 Configure Networking Automatically with DHCP or BootP to configure the device to connect automatically to a network, or 30 Configure Networking Manually to configure the device's TCP/IP settings yourself. | | 6. | Apply Your Configuration Changes
After all your configuration changes are complete, click the Apply Now button. None of your changes are made active until you click this button.
| NOTE If you attempt to switch to a different Preferences pane or close the System Preferences window, a confirmation dialog box appears prompting you to apply your configuration changes.
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