The most common problems with wireless connectivity are:

·          Unable to make a successful wireless connection

·          Intermittent connectivity

List out Updates and Hot fixes from Microsoft for Wireless Networking issues is available here.

Unable to Make a Successful Wireless Connection:

Being unable to make a successful wireless connection (from scanning to obtaining an IP address configuration) is the most common type of problem. The most common reasons are the following:

·        Mismatched configuration

·        Wireless Auto Configuration is enabled and a third party wireless configuration tool is installed

·        Wireless AP is performing MAC address filtering

·        Sources of signal interference

·        Sources of signal attenuation

Mismatched Configuration:

Many different properties of wireless connections must be matched between the wireless AP and the wireless client before a successful connection can be made. Some of the most common mismatches are the following:

·        Mismatched 802.11 technology

There are three different standards for 802.11 wireless networking that are in common use today: 802.11b, 802.11a, and 802.11g. Although a lot of recently manufactured wireless LAN equipment supports the use of more than one of these standards, it is still possible to get a mismatch. For example, a wireless network adapter that only supports 802.11a will not connect to a wireless AP that only supports 802.11b and 802.11g.

·        Mismatched authentication method

This is a very common problem. The wireless client cannot authenticate if it is not using the same authentication method as the wireless AP. Wireless authentication methods for SOHO networks include open system, shared key, WPA-PSK, and WPA2-PSK. Because the use of shared key authentication
is highly discouraged, that leaves open system authentication for wireless networks that are not WPA or WPA2-capable, WPA-PSK for wireless networks
that are WPA-capable, and WPA2-PSK for wireless networks that are WPA2-capable.

Verify the authentication method that is configured on the wireless AP and configure the Windows XP wireless client with the same authentication method.

For examples of configuring wireless networks for open system, WPA-PSK, and WPA2-PSK authentication, see Configuring Windows XP IEEE 802.11
Wireless Networks for the Home and Small Business.

·        Mismatched WEP keys

When using WEP encryption and manually specifying the WEP key, it is easy to incorrectly type the key. Mismatched WEP keys will not prevent an
association, but it will prevent any successful communication on the wireless network because the wireless client and the wireless AP will be unable to
interpret each other's frames. As a result, the wireless client will be unable to obtain an automatic IP address configuration or communicate with any network resource through the wireless AP. For example, a Windows XP with SP2-based wireless client will obtain an APIPA address and display "Limited or no connectivity" for the status of the wireless connection. To Troubleshoot "Limited or no connectivity" error click here.

The method of configuring the WEP key depends on the version of Windows on the wireless client.

o        For Windows XP with no service packs installed, you must type the WEP key (in the Network key field), specify the format for the WEP key
(either ASCII characters or hexadecimal digits in the Key format field), and specify the key length (either 40 bits or 104 bits in the Key length field).
You must match the WEP key for the proper format and key length to that which is configured on the wireless AP.

o        For Windows XP with SP1 or Windows XP with SP2, you must specify the WEP key twice in the Network key and Confirm network key fields.
You do not have to specify the key format or length because these are automatically determined from the typed key. For Windows XP with SP2,
you must select WEP in Data encryption.

When you use the Wireless Network Setup Wizard in Windows XP SP2, all the devices that support Windows Connect Now are automatically configured with the same WEP key.

·        Mismatched WEP key index

The WEP key index is a number that specifies which WEP key to use for the encryption of wireless frames. You can use up to four different WEP keys. In practice, only a single WEP key is used, corresponding to the first possible WEP key. The wireless AP and the wireless client must both be configured to use
 the first possible WEP key.

Specifying the first possible WEP key depends on how the wireless client and wireless AP begin numbering the four possible WEP keys. For example,
they could begin numbering them at 1 (from 1 to 4) or they could begin numbering them at 0 (from 0 to 3). In either case, choose the first possible value
on both the wireless client and the wireless AP. For example, Windows XP with no service packs installed begins numbering the possible WEP keys with 0. Windows XP with SP1 or Windows XP with SP2 begins numbering the possible WEP keys with 1.

·        Mismatched WPA-PSK or WPA2-PSK

If you are using WPA-PSK or WPA2-PSK authentication, you must configure a preshared key value in the Network key and Confirm network key fields. Verify that the WPA-PSK or WPA2-PSK value is the same as that which is configured on the wireless AP. For WPA, you must select TKIP in Data encryption and WPA-PSK in Network Authentication. For WPA2 with Windows XP with SP2, you must select AES in Data encryption and WPA2-PSK in Network Authentication.

When you use the Wireless Network Setup Wizard in Windows XP SP2, all the devices that support Windows Connect Now are automatically configured with the same WPA preshared key value. The Wireless Network Setup Wizard does not support the configuration of a WPA2 preshared key value.

Wireless Auto Configuration is Enabled and a Third-Party Wireless Configuration Tool is Installed:

Windows XP Wireless Auto Configuration provides integrated support for wireless networking and helps automate wireless configuration. Wireless network adapters also provide a wireless network configuration tool (for example Intel PROSet for Intel 2100B/2200B Wireless network cards). If the wireless network adapter driver supports Wireless Auto Configuration, installation and use of the network adapter vendor's configuration tool is not needed. To test whether your wireless network adapter supports Wireless Auto Configuration, right-click the wireless connection in the Network Connections folder and then click Properties. If there is a Wireless Networks tab, your wireless network adapter supports Wireless Auto Configuration.

 

Problems with initial configuration and connectivity can occur when Wireless Auto Configuration is enabled and the wireless network configuration tool is installed. In this case, both Wireless Auto Configuration and the wireless network configuration tool might be sending their settings to the wireless network adapter, resulting in configuration mismatches.

 

To solve this problem, use either Wireless Auto Configuration or the wireless network configuration tool, but not both.

For example, if there is a capability of your wireless network adapter that you must use and Wireless Auto Configuration does not support it (such as the configuration of a 152-bit WEP encryption key), then disable Wireless Auto Configuration and use the wireless network configuration tool. To disable Wireless Auto Configuration, clear the Use Windows to configure my wireless network settings check box on the Wireless Networks tab for the properties of the wireless connection in Network Connections.

 

If you decide to use the wireless network configuration tool supplied by the wireless network adapter vendor, then you must use this tool to specify all of your wireless network settings (such as the wireless network name, and authentication and encryption settings), rather than using the properties of a wireless network from the Wireless Networks tab.

 

If you want to use Wireless Auto Configuration, then remove the wireless network configuration tool using Control Panel-Add or Remove Programs or some other means provided by the wireless network adapter vendor, such as uninstall option available via the Start menu.

Wireless AP is Performing MAC Address Filtering:

Some wireless APs allow you to specify the set of 6-byte media access control (MAC) addresses that are allowed to send frames to the wireless AP. MAC addresses are also known as hardware or physical addresses. This feature is known as MAC address filtering and is designed to provide an extra layer of security for wireless networking. However, an attacker can easily thwart this extra security by capturing the frames sent to or from an allowed wireless client and reprogramming their own wireless network adapter to use a valid MAC address.

 

If you want to use MAC address filtering, ensure that the MAC address filter list includes all of the MAC addresses for all of the wireless network adapters installed in all of the wireless clients on your network. If you install a new wireless network adapter, you must update the MAC address list to include the MAC address of the new adapter.

 

If you do not want to use MAC address filtering, ensure that it is disabled on the wireless AP.

Sources of Signal Interference:

IEEE 802.11b and 802.11g wireless networks operate in the 2.4-2.5 GHz S-Band Industrial, Scientific, and Medical (ISM) frequency range that is used by other types of wireless devices such as cordless phones, baby monitors, home security and monitoring systems, Bluetooth-enabled devices, and wireless video cameras. Other types of devices that are not wireless but produce signals in the S-Band ISM include microwave ovens. If you have sources of interference, it might not be possible to successfully connect with a wireless AP.

 

To verify whether signal interference is the problem, temporarily turn off or otherwise disable the possible sources of interference and try to connect to your wireless network. If it is not possible to disable a source of interference, such as a security system, then move the wireless client and wireless AP away from the house or office and attempt the connection again.

Sources of Signal Attenuation:

Walls, ceilings, and the presence of metal or shielding between wireless clients and the wireless AP can cause wireless networking signals to attenuate, or lose their strength. In some cases, the signal loss is complete, resulting in the inability to make a wireless network connection.

 

To verify whether signal attenuation is the problem, set the wireless client in the same room as the wireless AP with a clear line of sight to the wireless AP. Try not to set the wireless client too close to the wireless AP because, depending on the design of the wireless AP's antenna, you might be placing the wireless client in the wireless AP's signal shadow. Try to connect from different locations in the room.

Checking the signal strength:

1.   Click Start and select Control Panel.

2.   Click Network and Internet Connections. The Network and Internet Connections window opens.

3.   Click Network Connections. The Network Connections window opens.

4.    Double click Wireless Network Connection.

5.   Select Status. The Wireless Network Connection Status dialog box opens. The meter registers the signal strength for wireless Ethernet on your notebook if other computers with the same network name are within range of your notebook.

Change the power Management settings:

·         Click Start -> Control Panel -> Network Connections.

·         Right-click the Wireless Network icon, and choose Properties.

·         Click Configure. Select advanced tab, Choose Power Management. Uncheck default value, and move the slider to highest or pick Power Save Mode, and select Disable under Value.

[Still experiencing Weak Signal strength – Try these Tips]

Intermittent Connectivity :

In some cases, it is possible to initially obtain a successful connection, but the wireless connection is automatically disabled or disconnected without user intervention. The most common causes are the following:

·        802.1X authentication is enabled on the wireless client and not the wireless AP

·        Duplicate wireless network name

·        Sources of signal interference

·        Sources of signal attenuation

·        Computer viruses

·        Faulty hardware or outdated wireless network adapter drivers

802.1X Authentication is enabled on the Wireless Client and Not the Wireless AP:

By default, 802.1X authentication is enabled on all wireless and wired network connections. In Windows XP SP1, Microsoft changed the authentication process for wireless networks. If 802.1X authentication is enabled and 802.1X authentication does not complete properly, the connection is dropped. This typically happens three minutes after the connection has been made using open system authentication.

 

To correct this problem for computers running Windows XP with SP1, do the following:

 

6.   Click Start, point to Settings, and then click Network Connections.

7.   In Network Connections, right-click your wireless connection and then click Properties.

8.   Click the Wireless Networks tab. 

9.   Under Preferred networks, click your wireless network name, and then click Properties.

10.Click the Authentication tab, and then clear the Enable IEEE 802.1x authentication for this network check box.

11.Click OK twice to accept the changes.

This procedure is typically not required for computers running Windows XP with no service packs installed or Windows XP with SP2. However, it is usually a good idea to verify that 802.1X authentication is disabled when you are using open system authentication. For Windows XP with SP2, use the previous procedure. For Windows XP with no service packs installed, do the following:

 

1.   Click Start, point to Settings, and then click Network Connections.

2.   In Network Connections, right-click your wireless connection and then click Properties.

3.   Click the Authentication tab, and then clear the Enable network access control using IEEE 802.1x check box.

4.   Click OK to accept the changes.

Duplicate Wireless Network Name:

One of the reasons for intermittent connectivity is that your wireless network name has been duplicated with another separate wireless network within range of your wireless clients. For example, you might live in an apartment building and your wireless network overlaps with another wireless network with the same wireless network name above or below your apartment. In this configuration, all of the wireless APs that are advertising the same wireless network name are considered as belonging to the same wireless network. In this case, it is possible for your wireless client to choose the wireless AP of another wireless network over your own wireless APs. If your wireless client is not configured for the authentication method and keys of the other wireless network, then you can experience intermittent connectivity problems, until your wireless client chooses one of your wireless APs again.

 

Duplicate wireless network names can result when multiple wireless networks are set up using the default wireless network name as configured on the wireless AP.

 

To prevent this problem, always change the default name of the wireless network when initially configuring the wireless AP.

 

To verify that your wireless network is not being duplicated by another wireless network that is within range of your wireless clients, disable or turn off your wireless APs. Then, use a computer running Windows XP to scan for the available wireless networks. If your wireless network name appears in the list of available networks when your wireless APs are turned off, then you have a duplicate wireless network name. Reconfigure your wireless AP for a new and unique wireless network name (also known as an SSID).

Preventing other Wireless Networks from being detected:

1.      Click Start, then select Control Panel.

2.          Click Network and Internet Connections. The Network and Internet Connections window opens.

3.          Click Network Connections. The Network Connections window opens.

4.          Right-click Wireless Network Connection and select Properties. You should see a similar window shown in the figure below.

5. Click Advanced button found under Wireless Networks tab and uncheck Automatically Detect Non-Preferred networks.

6. Click close and then Ok.

Sources of Signal Interference:

Just as sources of signal interference can cause a lack of connectivity, they can also cause intermittent connectivity problems when the device causing the interference is running. Devices such as microwave ovens, baby monitors, and cordless phones can cause intermittent wireless connectivity problems when they are running.

 

To determine whether a source of signal interference is causing intermittent connectivity loss, try to correlate the times of connectivity loss with the times that a device causing signal interference is being operated. For example, does the connectivity loss occur whenever someone uses the microwave oven or when the baby monitor is turned on in the evening?

Sources of Signal Attenuation:

Just as sources of signal attenuation can cause a lack of connectivity, they can also cause intermittent connectivity problems when the object causing the attenuation is moved. To determine whether a source of signal attenuation is causing intermittent connectivity loss, try to correlate the times of intermittent connectivity with the times that an object that might cause signal attenuation is moved. For example, does the intermittent connectivity occur whenever someone opens the large metal door between the garage and the kitchen?

Try changing the MTU speed to prevent any packet loss:

 

Change the Maximum Transmission Unit (MTU) Size:

http://www.winguides.com/registry/display.php/280/

HOW TO: Change the PPPoE MTU Size in Windows XP:

http://support.microsoft.com/default.aspx?scid=KB;en-us;283165&

Computer Viruses:

Some computer viruses are known to cause intermittent connectivity problems for wireless connections. Ensure that you have the latest antivirus signature for your antivirus software and perform an antivirus scan of your entire computer to eliminate this possibility.

Faulty Hardware or Outdated Wireless Network Adapter Drivers:

Another cause for intermittent connectivity is that the wireless AP or the wireless network adapter is faulty. This issue can be difficult to determine. Run any diagnostic facilities of your wireless AP or wireless network adapter to determine that they are operating properly. Ensure that you have installed the latest version of the wireless network adapter driver in Windows XP.

Here is a quick checklist that should resolve most of the problems with wireless connections for a SOHO wireless network:

1.   Verify that the wireless AP plugged in and operating. For example, check for indicator lights on the wireless AP.

2.   If the wireless AP is also your router to the Internet, verify that the router's wireless capabilities are enabled.

3.   Verify that your wireless AP and all of your wireless clients use a common 802.11 standard, such as 802.11a, 802.11b, or 802.11g.

4.   Verify that the wireless network adapters installed on your wireless clients are properly plugged in and enabled. If a wireless connection corresponding to the wireless network adapter appears in the Network Connections folder, then the wireless network adapter is properly plugged in. If the wireless connection has been disabled, it will display Disabled in its status under the wireless connection's name in the Network Connections folder. To enable the disabled wireless connection, right click it and click Enable.

5.   Verify that you are using the latest version of the wireless network adapter driver that is available from Microsoft or the wireless network adapter vendor. To obtain the version of the wireless network adapter driver that is installed, right-click the wireless connection in the Network Connections folder. On the General tab, click Configure. From the wireless network adapter properties dialog box, click the Driver tab. The version of the wireless network adapter driver is displayed next to Driver Version. If your wireless client is connected to the Internet, click Update Driver to launch the Hardware Update Wizard and search Windows Update for a newer version of the driver. Alternately, check the wireless network adapter vendor's Web site for a newer version of the driver.

6.   Verify that the wireless AP and your wireless clients are configured for the same authentication method (open system authentication, WPA-PSK, or WPA2-PSK).

7.   Verify that the wireless client is within range of the wireless AP and that there are no sources of signal interference or attenuation that could prevent successful connectivity.

8.   Verify that you are using either Wireless Auto Configuration or a wireless network configuration tool provided by the wireless network adapter vendor, but not both. If you are not using a wireless network configuration tool, verify that the Wireless Zero Configuration or Wireless Configuration service has been started using the Services snap-in available from the Administrative Tools folder.

9.   For WEP encryption, verify that the wireless AP and your wireless clients are configured with the same WEP encryption key (using the same key format and for the same key length). When you use the Wireless Network Setup Wizard in Windows XP SP2, all the devices that support Windows Connect Now are automatically configured with the same WEP key.

10. For WEP encryption, verify that the wireless AP and your wireless clients are configured to use the first possible WEP key.

11. For WPA-PSK authentication, verify that the wireless AP and your wireless clients are configured with the same WPA preshared key value (using the same key format and for the same key length). When you use the Wireless Network Setup Wizard in Windows XP SP2, all the devices that support Windows Connect Now are automatically configured with the same WPA preshared key value. For WPA2-PSK authentication, verify that the wireless AP and your wireless clients are configured with the same WPA2 preshared key value (using the same key format and for the same key length).

Happy networking.

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