Fix hardware and configuration issues common to wireless LANs

Fix hardware and configuration issues common to wireless LANs

Both the money savings and the ease of use of wireless LANs are beneficial to small offices—until something goes wrong. Then it becomes all too apparent that, while wireless networks are growing, troubleshooting resources for wireless LANs are not.

When a wireless network fails, there are a few key areas to look to first. Let's look at some of the more common hardware problems that can cause a wireless network to fail. I’ll also cover the configuration issues that can plague a wireless LAN. With this information, you can troubleshoot your wireless network with confidence. (This article assumes that you’re troubleshooting an infrastructure network, and not an ad hoc network.)

Hardware troubleshooting:

When you have only one access point and only one wireless client that are having connection issues, then you’ve already determined the scope of the problem: Your one client is having trouble attaching to the network. But if you have a larger network, determining the scope of the problem becomes a little more involved.

If lots of users are having trouble connecting but there are still some users who are able to work, the problem is most likely that your network has multiple access points and that one of the access points is malfunctioning. Often, you can take an educated guess as to which access point is malfunctioning by looking at the physical locations of the users who are having the problem, and then figure out which access point serves that portion of the building.

If no one can connect to the wireless network, there are several things that could be going on. If your network uses a single wireless access point, it's possible that the access point could be malfunctioning or could contain a configuration error. The problem could also be related to radio interference or a break in the physical link between the wireless access point and the wired network.

Check connectivity to the access point:

First, you should perform a communications test to see if the access point is responding. Open a Command Prompt window on a PC on your wired network and ping your wireless access point’s IP address. The wireless access point should respond to the ping. If it doesn’t, there’s either a break in the communications link or the access point is completely malfunctioning.

To figure out which is the case, try pinging the access point’s IP address from a wireless client. If the wireless client is able to ping the access point successfully, the problem is almost certainly a broken communications link, such as a damaged cable.

If the wireless client is unable to ping the access point, the access point could be malfunctioning. Try unplugging the access point to reset it and then plug it in again. Wait for about five minutes and then try pinging the access point from both the wireless and the wired clients again.

If both pings still fail, it is likely that the access point is damaged or has an invalid configuration. At this point, I recommend focusing your efforts on getting the access point to communicate with the wired network. Plug the access point in to a known-good network jack using a known-working patch cable. You should also verify the access point’s TCP/IP configuration. After doing so, try pinging the device from a wired client again. If the ping still fails, the unit has probably been damaged and should be replaced.

Configuration issues:

I’ve found that wireless networking equipment is fairly reliable, and the vast majority of problems are related to the network’s configuration rather than a hardware malfunction. With this in mind, let's look at several common hardware configuration problems that lead to a disruption of wireless services.

Test the signal strength:

If you can ping the wireless access point from a wired client but not from a wireless client, the access point is probably just experiencing a temporary problem. If the access point continues to have problems, I recommend checking the signal strength. Unfortunately, there’s no standard method for doing this. Most wireless NIC manufacturers, however, include some mechanism with the NIC for measuring signal strength.

Try changing channels:

If you determine that you’re getting a weak signal but nothing has physically changed in your office, attempt to change channels on the access point and on one wireless client to see if a different channel improves the signal strength. I run a wireless network in my home office, and I’ve found that one of my cordless phones interferes with my wireless network when the phone is in use. 802.11b wireless networks function on the 2.4-GHz frequency, just like many higher-end cordless phones. Changing channels on all of your wireless clients can be a big undertaking, so I recommend testing the new channel with one client first. Remember that your problem could go away as soon as someone hangs up a phone or turns off a microwave oven.