After we upgraded WLC from rel 8.2 to 8.5 we had a bunch of WiFi printers not able to associate anymore to our Cisco APs.
Seeing that these printer are very important for the production flow, we had to perform a downgrade to the previous release and luckily the roll back solved the issue.
Anyway for more then one reason we ought to perform this upgrade, so we prepared a lab to better understand what happened and find a solution.
TAC eng confirmed the different behavior but, using debug, he saw AP replied to every Probe Request with the relative Probe Response, so for him all seemed to be fine and was not able to undestand the reason for the missing association by the printer.
We didn't give up and using a WiFi sniffer and capturing traffic between APs and Printers with both releases, we discovered "Probe Response" packets from AP to client had different sizes: the 8.5 rel. adds indeed 4 new TAGs in the IEEE 802.11 portion of the frame and Wireshark was even not able to decode one of them marking it as "unknown".
Probably printer considers the AP's response as a malformed packet due to this "unknown" field and discards it.
We guessed these TAGs are sent for compatibility with Aironet clients and in the lab enviroment we tried to disable the feature in the SSID configuration on WLC. At this point lab printer was able to associate normally to AP.
Now we would like to disable this features in the production env. but before to do that we would like to check if any clients currently associated is using it and could have issue without it.
Is there any show and/or debug command able to show us if Aironet Extension is used by any client connected to our WLC ?
PS the issue has been tested on 2500 3500 and 5500 WLCs with same behavior.
We have to admit printer is a very old model but is working fine with 8.2 and also with 8.5 after "workaround".
