Resolving SSID Conflicts in Windows XPby Wei-Meng Lee, author of Windows XP Unwired
Windows XP comes with the Wireless Zero Configuration feature, which allows a computer to join a wireless network without any need for configuration. Using Wireless Zero Configuration, you will automatically connect to a wireless network if one is present. If there are multiple wireless networks present, Windows XP will automatically associate with the access point that has the strongest signal.
However, one problem arises when two or more wireless networks have identical Service Set Identifiers (SSIDs).
A SSID is used to identify a wireless network. In a large wireless network deployment, multiple access points are used, and it is common for all these access points to be configured with the same SSID to facilitate roaming (allowing your computer to associate with any access point as you move about). However, two different wireless networks can also be configured with the same SSID -- for example, your home wireless network may use the same SSID as your neighbor's.
Windows XP will only report the presence of one SSID. But which wireless network do you join? The answer depends on where you are situated at the moment; Windows XP will associate with the access point nearest to you (which has the strongest power). So there isn't any choice for you to choose which wireless network to join. This is a known problem in Windows XP.
As an example, in my test environment, I have two access points, each configured with the same SSID ("Home"). Figure 1 shows Windows XP showing only one SSID.
|Figure 1. Windows XP displays only one SSID for two different wireless networks with the same SSID|
In this case, when you choose to connect to the "Home" wireless network, you do not know to which access point you are connecting.
Turning Off Wireless Zero Configuration
Wireless Zero Configuration is implemented as a service in Windows XP. And so, turning this service off can prevent automatic association from happening. To do so:
- Go to Start->Settings->Control Panel->Administrative Tools->Services.
- Double-click on Wireless Zero Configuration (see Figure 2).
- Change the Startup type to Manual (so that the service will not be started when the computer is rebooted) and click on the Stop button to stop the service (see Figure 3). Click on OK to complete the process.
|Figure 2. Locating the Wireless Zero Configuration service|
|Figure 3. Stopping the Wireless Zero Configuration service|
With Wireless Zero Configuration service turned off, Windows XP will not be able to detect the presence of wireless networks automatically. For this, you need to rely on the utility provided by your wireless card/adapter.
For example, I used the WLAN Monitor provided by Linksys for my Linksys wireless card, and it is able to detect the presence of the two wireless networks in my environment (see Figure 4).
|Figure 4. The Linksys WLAN Monitor|
To connect to a network, I can now simply select the one that I want to connect to (you can differentiate the two access points by looking at their MAC addresses) and click the Connect button.
This is really a case of Windows XP not immediately revealing the true flexibility it has for connecting to various networks. But as is so often the case, with a few adjustments, you're back in control.
Wei-Meng Lee (Microsoft MVP) http://weimenglee.blogspot.com is a technologist and founder of Developer Learning Solutions http://www.developerlearningsolutions.com, a technology company specializing in hands-on training on the latest Microsoft technologies.
Return to the Wireless DevCenter