Typically the LED on Cisco Aironet wireless access points glows a soothing blue color if a client is associated, or a steady green if it is patiently waiting for someone to join it’s network and share its amazing WLANs. Today I ran across an interesting problem that I hadn’t seen before. One Cisco Aironet 3502e access point had an LED was not lit. Typically, this happens when an access point is not getting power. It is usually caused when the AP is unplugged or has a power supply that is bad. In this case, the access point was powered by power over ethernet (POE), and I could tell that it was getting power (the command ‘show power inline’ on a Cisco switch will tell you which switchport is supplying power and how many watts are being consumed). The switch also showed it’s status was ‘connected’ so I knew it had a valid ethernet link. Hmmm..strange. The Cisco Wireless Lan Controller (WLC) also showed the access point as booted up, connected and generally happy. Why no LED? Weird…. Then I shamefully fell into the old windows method of troubleshooting: “When all else fails, reboot!” I disrupted the power to this remote access point by shutting down the switch interface and brought it back up, but it still had no LED light, not even during the reboot. (At that point I may have uttered an obscenity under my breath, but don’t tell anyone.) Since this access point was around 1000 miles away and over 20 feet off the ground, I didn’t really want to tell the end user to get on a lift and swap it out, and I didn’t want to tell them it was working fine as it obviously wasn’t from their perspective. I did a little research and found there is a bug in Cisco’s access point code that causes the LED light to disable itself. Nice. Luckily the fix is easy, and it doesn’t require a software upgrade. Just run the following command from the CLI of the Wireless Lan Controller (WLC).
wlc>config ap led-state enable all
That fixed it for me. Happy blue and green lights for the end-user, another satisfied customer for me. Hopefully you can get similar results if you run across the same problem in your wireless networking troubleshooting adventures!
