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Some Clients unable to connect after WLC upgrade from 8.2 to 8.5 due to AIRONET support

Emiliano Luca
Level 1
Level 1

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".

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