Skip to main content

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.


Comments

Post a Comment

Popular posts from this blog

Finding WLAN issues from the Windows Client Side

What happens when you've done everything from the wifi side of diagnosis a problem dare I say a ghost problem? What if the situation within your network seems perfect, you can't find anything in packet captures, Prime or off your WLC - What other options do you have?  Luckily, I found plenty! One of the handiest tools I like to use when onsite and starting to check clients out is the NETSH command in command line. Doing a roaming analysis via the client versus on Prime isn't a bad thing some days to give you a real world perspective of when roams happen.  Of course, client debugging in WLCs help too but I figured I'd show you what I do when walking around with a laptop to see the BSSID you are connected to. I use  netsh wlan show interface  Which outputs this:     Name                   : Wi-Fi     Description            : Marvell ...
2 comments
Read more

Quickly and Freely convert a DWG file to a PNG for Ekahau

DWG to PNG Free and Quick! One of the problems that we run into many times with Ekahau is the size of the file that has been converted from a DWG file.  While a desktop with some horsepower (CPU, GPU, RAM) can power through it we may notice that during a Survey that there may not be enough power. What do I mean?  I think most have experienced it but when you start moving around on the map, things lag - it feels that the picture takes for ever to rasterize on the screen. This is a part of what I believe needs to be done before you get onsite and before you step of your house to start a survey. LOAD THE ESX file that was used in the design and test the speed on the device you will be surveying with.  If you are noticing acting like Google Chrome (aka resource hog) then you should probably recreate the file unless there is an explicit need to use the original design ESX file. So now the situation is this - you have the DWG file, you know that if you load it that you are goin...
Post a Comment
Read more

Pull all AP names from a Cisco WLC easily

How to collect AP Names from a Cisco WLC So if you are running into this, you've likely have already worked with spreadsheets that help auto-populate commands.  It's pretty simple to create these but I'll give you a little screenshot of a basic use of this in Excel. Put the AP name in A1 of Excel Then create a colum with =CONCATENATE("config ap primary-base NAME-HERE  ",A1, " 192.168.1.1") This will create the command of "config ap primary-base APNAME1 192.168.1.1" You can then fill in A2, A3 with the rest of the names.  This is useful if you are pulling AP's from one controller to another. This allows you to create a command list to make instant changes by cutting and pasting into SecureCRT, Putty or whatever your program of choice is. The first area in black would be the WLC Domain name (WLC01-5520) and the second black part would be the IP (192.168.1.1) as an example. But what if you don't have the list of AP names?  What do you do? ...
Post a Comment
Read more