After setting up a new Cisco Wireless LAN Controller (WLC), I decided to go ahead and setup a spare Cisco Lightweight Access Point (LAP) to connect to it. I did so by changing DHCP option 43 to point to the new WLC instead of the old one for that DHCP reservation. I plugged in the AP and… Damn, it still connected to the production WLC. I rebooted it again, and then a third time. After multiple restarts it was still connecting to the production WLC time and time again. I even went so far as to setting the LAP’s primary controller to point to the new WLC. Still, it failed to register with the new WLC and instead kept hitting the production one.
That’s when I remember, LAPs can use a DNS record to find the WLC they’re supposed to use if it can’t find one via DHCP option 43. I fire up DNS and sure enough, there are the two entries:
Both were A records pointing to the production WLC. Since every subnet our LAPs are a part of use DHCP option 43, it wasn’t completely necessary for these records to be around. Thinking that was the cause of my problems, I went ahead and removed the records. After waiting a few minutes for DNS to propagate to the other DNS servers, I rebooted the LAP one more time. This time it didn’t connect to the production WLC. Success! Or was it?