I had a few Cisco 3502e access points that I needed to deploy temporarily and came across one that wouldn’t join the wireless LAN controller. After the AP powered up the status LED would flash green, then red, then off, and then repeat. The “Getting Started Guide for Cisco 3500 Series Access Points” on Cisco’s website said that this meant “Discovery/join process in progress”. I’d not seen that happen to any of the other identical AP’s I’d just worked on, and after letting it sit there a while I determined that it wasn’t going to sort itself out.
Over on the “Goat Networking” blog there was a post that offered an explanation as to what was happening and what to do to fix it. Specifically, I needed to connect to the AP via serial cable to get a console connection, get into privileged mode (BTW, the default Enable password is “Cisco”, and it’s case sensitive) and run this command:
lwapp ap controller ip address XXX.XXX.XXX.XXX (this is the IP address of your WLAN controller)
After a few seconds the AP will again attempt to reach out and find a WLAN controller, and this time it’ll connect successfully and determine if any code updates need installing before joining the controller.