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.

[Andre_Brits_Kan]

Hi FES my environment is very simulator to yours but with a twist.
The client of ours is also a university and the system is being used for BYOD exams.
So students can write on their own devices, we apply a policy limiting access to only VM Ware VDI desktop to for exams.

You should see a 3rd year medical student get disconnected half way through the exam = very unhappy 

[FES]

We think that this post is wrong, 9.21.08 doesnot solve the problem
https://gtacknowledge.extremenetworks.com/articles/Solution/Client-connection-issues-with-firmware-9...

If you configure Broadcast re-key interval to 60 sec (or 30) you have continuous disconnections of the clients.
I have dissabled this option and we dont have this disconnections... we are testing if this change is stable and no more disconnections of our testing clients occurs.
we'll say you tomorrow

[Chat]

Maybe this point could affect to excessive battery consumption in the connected devices... we'll have to test this points.

thanks

[FES]

yes, if was a test enviroment. I have read that this problem was present ir other frabicants with the same devices. One solution was increase the rekey time to the max... one day in seconds.
thaks for the reply Jason

[Jason1]

FES,

Is that with the re-key set to disabled?
I was going to suggest setting that to 3600 with 9.21.08, that is the default setting.

Regards,
Jason