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Chapter 4. Connecting Your Computer > Creating an Ad Hoc Wireless Network

Creating an Ad Hoc Wireless Network

Wi-Fi devices support two networking modes: the infrastructure mode in which clients attach to access points acting as central routing points, and a more informal mode called ad hoc, which means, in this context, “for a particular purpose at hand.” Ad hoc networks are created among two or more machines that then act as if they're on the same tiny network.


Ad hoc networks can be routed to another network, such as an Internet-connected dial-up or Ethernet network. We discuss this in “Creating a Software Access Point” in Chapter 5, Building Your Wireless Network.

No one machine maintains the network, but it remains in effect as long as any machine is in ad hoc mode. A network of one is pretty lonely, though.


Ad hoc networking may not work correctly among wireless network adapters sold by different companies before 2002. See Chapter 3, How Wireless Works, for more on this topic.

How you enable ad hoc mode on your computer varies depending on the operating system and software. Typically, you enable a setting in the client software that turns on “computer-to-computer networking” or “ad hoc mode” (different manufacturers use different names). You must also pick a channel over which the two computers will connect, but once you set a channel, other computers will find it automatically. You can almost always enable WEP encryption over an ad hoc connection.


Luckily, you don't have to configure your network settings when all you're doing is connecting a pair of computers to each other in ad hoc mode. That's because both Windows XP and Mac OS since 8.6 support a standard method of choosing IP addresses that don't conflict.

Creating an Ad Hoc Network in Windows XP

The process of creating an ad hoc network in Windows XP requires a number of steps, but they're not difficult to carry out.

From Control Panels, select Network Connections, and then open the Wireless Network Connection dialog.

Click Properties.

Click the Wireless Networks tab.

Click Advanced at the bottom of the window.

Select Computer to Computer (Ad Hoc) Networks Only, and deselect Automatically Connect to Non-Preferred Networks (Figure 4.25).

Figure 4.25. Creating an ad hoc network in Windows XP.

Click Close.

Click the Add button under Preferred Networks.

Enter a network name for your ad hoc network (Figure 4.26). (Note that Windows identifies the connection as ad hoc in the bottom of the window using a strange method of a checkbox option that's selected but dimmed and disabled.)

Figure 4.26. Configuring a Computer to Computer network in Windows XP.

Set any WEP options you want.

Click OK.

In the Preferred Networks list, you now see your network with a PC Card icon next to it to indicate it's an ad hoc network. A red X brand on the icon indicates no other computers are yet connected.

Other Windows XP clients see this network in their list of Available Networks with the same PC Card icon.

Creating an Ad Hoc Network with a Mac

Under Mac OS 8.6, 9.x, and X, creating an ad hoc network is a simple operation:

  • In Mac OS 8.6 or 9.x, open the AirPort application, click the Settings expand triangle to show the extra settings, and choose Create Computer to Computer Network from the Choose Network pop-up menu in the AirPort Network section (Figure 4.27). In the Computer to Computer dialog that appears, name your network. If you want to assign a password or change the default channel, click More Options and enter the desired information. Click OK when you're done. (Figure 4.27 shows a Fewer Options button because we've displayed the extra options!)

    Figure 4.27. Creating a Computer to Computer network in the Mac OS 9 AirPort application.

  • In Mac OS X, choose Create Network from the AirPort menu in the menu bar or from the Network menu in the Internet Connect application. Either way, in the Computer to Computer dialog that appears, enter a name for your network and pick a channel. If you want to password-protect your ad hoc network, check the Enable Encryption (Using WEP) checkbox and enter your password (Figure 4.28).

    Figure 4.28. Creating a Computer to Computer Network in Mac OS X.

Once you've created an ad hoc network, other people connect to it just as they would to any other wireless network, whether they're using Macs or PCs.

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