How to fix a Cisco IP that has been stranded after a migration due to static IP settings

If you are reading this - I'm going to assume you are familiar with two things.

1. How the CAPWAP Process Works.  If not read: http://www.revolutionwifi.net/revolutionwifi/2010/11/capwap-controller-discovery-process_23.html

2. How bad of an idea it is to assign static IP addresses to APs on your Cisco WLC network. If not read: Just don't.

So I was brought onto a call.  There are migrations going on where the network consists of APs in a large spread out geography and was designed utilizing Flexconnect.  These APs are moving from one controller to another as well as a redesigned address space.

You'd think - Well, this won't be so bad with CAPWAP and DHCP.  You are right butttttt everyone forgot to run on the WLC config ap static-ip delete (ap name or all) or couldn't do this because they needed the AP to the last minute before the cut-over.  You could also accomplish this in the GUI.

What happens when a cut-over has been fully completed and the APs were never checked?  Do you know what happens when you assign a static IP to a CAPWAP AP?  It will NEVER find home on a new address space and DHCP of course, won't work.

You also can't migrate back because everything else has been switched over and that would just be the lazy and long way to do this.

So - how do you fix this?  It's easy to think that a mode button reset would fix this.  You are right, it would but what happens if this AP is in Buenos Aires and there is not a single technical person onsite or the AP is mounted 30ft on a ceiling only accessible via scissor left?

This situation really sucks now!

What do you do?

Here is a work-around that I thought up with the help from https://mrncciew.com/2013/05/04/wlc-discovery-via-broadcast/ MRN-CCIEW's blog (Which I highly recommend)

You should at least have the only static IP and if not, CDP Detail will tell you!

Now you have that IP/Mask.  

1. Create a VLAN with the range.

2. Switch the access port on the switch to where your AP is location to that new VLAN

3. ip helper-address x.x.x.x (Your WLC IP)

4. ip forward-protocol udp 5246

This will allow the AP with the static IP to figure out how to get to your controller.  Once CAPWAP completes, you'll have the ability to change the primary/secondary WLC addresses and then clear the static IP.  Realize you'll lose connectivity after clearing the static ip config!

Now change that switchport's VLAN back to the proper access VLAN with DHCP and you are now done and did not need physical access to the AP to do this.

Now you can rest assured you don't have to figure out how to catch a flight to Argentina.