When tracking down client connection issues, the problem often is either a misconfigured client or access point. First, however, you should make sure that there is not a physical problem with your AP or APs.
When you are in an environment with multiple clients and APs, finding out what is wrong can be a chore. For example, if you have many userssome of whom are able to connect to the WLAN, others who are notyour most likely culprit is a misconfigured AP. How do you know which AP to fix?
You can look around your office and make a good guess about which AP is malfunctioning. If the users who cannot access the WLAN work in the same area, you should look at the AP servicing that area.
Don't overlook the obvious.
Sometimes an AP gets unplugged or the circuit breaker has been turned off. It sounds obvious, but make sure there is power to the AP.
In addition, a client adapter that is not Wi-Fi certified is a good sign of trouble ahead. Vendors who are eager to ship product don't always ensure that their products are compatible with other manufacturers' devices. As such, if an adapter has not been Wi-Fi certified, it might not work with other companies' APs. Cisco products are Wi-Fi certified.
It has been mentioned previously, but bears repeatingIs there any radio interference? (For example, a new cordless telephone or a new WLAN might have been installed in the neighboring office.) Don't overlook the potential for bad wiring between your AP and the switch. Also don't miss such simple issues as a power cable coming loose from the AP.
Check the AP
Perform a communications test to see if the AP responds. You can do this with the basic ping command. You should attempt the communications test twiceonce on the wired network and once on the wireless network. If you are not familiar with the test, it is an easy, two-step process:
Begin by pinging the AP from a PC on the wired network. If the AP does not respond to the ping test, there is a break in the communications link or the AP is misconfigured. You can determine which is the problem by repeating the ping test on a wireless client. If the wireless client can successfully ping the AP, then you know there is a communications link problem between the AP and the wired network. You might have to run new Category 5 cabling to the AP.
If the ping from a wireless client is unsuccessful, the AP might be faulty. Unplug the AP to reset it, and then reconnect the power. If you can do it without affecting users, reset the switch the AP is connected to. Give the AP a few minutes before you try to ping it again; this gives the network time to recognize the AP. Run the ping test from both wired and wireless networks again. If both tests fail, the problem might be either a faulty AP or a misconfigured AP.
The best way to determine if your AP is damaged is to plug it into a jack you know works using a patch cable you know is not damaged. Also verify the AP's TCP/IP configuration. The AP's IP address can be found on the Express Setup page. When you have done this, try to ping the device from a wired client. If the test still fails, the AP is probably damaged and should be replaced.
APs tend to be reliable devices, so before calling your AP's vendor with your warranty in hand, take a closer look at the AP's configuration. This tends to be where the bulk of the problems exist.