Wireless clients sporadically getting Limited Connectivity, APs dropping packets

[John_Rowler]

We have a pair of V2110 wireless controllers and around 400 3825i access points. Controller firmware is 09.21.06.0002. AP firmware is 9.21.27.1387X.

About 4 months ago we noticed a problem where the APs would just drop traffic. A packet capture will show a ping coming into the radio from the client, going out the Eth interface on the AP, the reply coming back into the Eth interface, and never going out of the radio.

A particularly strange detail is that this only happens with certain source/destination traffic. For instance a client cant ping the gateway of 10.1.20.1/24. but cannot pint the server at 10.1.20.2. Since we can see the ping making it to the server and the ping reply making it back to the AP, we know it's not a firewall/ACL/routing issue on any other part of the network. The traffic disappears at the AP. Clients cannot communicate with anything on the Internet or any of our servers (DNS, DHCP, etc.) during this time. They can ping gateways in any subnet but that's it; everything else is failed.

More details:

-We've gone through several firmware updates with GTAC. Nothing has helped.
-The issue can affect any client on any AP in any location at any time.
-The issue is intermittent; it may happen every few minutes or once per month to a particular client in a particular area. Once failed it may last for seconds or days.
-While it's affecting one client, other clients on the AP may be working fine or may also fail.
-It can happen on either 2.4 or 5.7GHz.
-It can affect any type of client (phone, laptop, tablet) and any OS.
-Restarting the client or AP will sometimes fix the issue, sometimes not.
-It happens with our without using NAC, or any other type of authentication. It happens on completely open networks as well.
-It happens on both bridged at AP and bridged at controller topologies.
-It's not limited to a particular subnet or VLAN.
-It happens with or without Flexible Client Access enabled.
-It happens on either controller.
-GTAC hasn't made much progress on the issue in 4 months.

[John_Rowler]

Nope, the only way to see it for sure is to catch a client while it's failing. It's often working by the time we get to the room, and fails again just after we leave. Very frustrating.

[JP4]

Are you able to tell in anyway on the back-end through AP traces/logs or anything like that when it happens ? I originally thought our problem was limited to 2.4ghz, but I think that was another issue that was corrected in earlier 9.21 code. We have had some students express frustration with wifi at times recently and I have been working with them and it seems like most of them point back to the issue discussed here.

[John_Rowler]

It happens often. We have hundreds of open calls, with most of those users being affected daily.

[Doug]

We have many beta test accounts where code 9.21.07 has fixed connection issues. I would suggest anyone that is still having issues post 9.21.07 to please contact or continue to work with GTAC support to iron out any site specific problems.

[JP4]

How often is the problem happening for you ? We have been getting reports of students having internet problems, but the more I talk with them, it seems like it is more wide-spread for us than I originally thought. Disappointed to here that 9.21.0.7 did not fix the ongoing issue. What's next ?