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.

[JP4]

our radius server is connected back to ldap so I don't have individual user accounts. I will take a look and see how it compares though. Not something I have looked at recently.

[Doug]

JP for a test, open the RADIUS users file:

You add Session-Timeout to the user accounts:

Example:
User Doug
Password = "Doug"
Session-timeout=1800 (seconds)

[Doug]

Just a heads up, the fixes included in 9.21.08 will be added to 10.01.04 which should be available on our download site early next week.

Reference: Client connection issues with firmware 9.21.07 or 10.01.03

[JP4]

FES, what file has the the setting for the radius timeout value you changed ? We are also running freeradius and I would like to check this on our system for comparison.

[FES]

Ckeck if you have the Key Management Options (Privacy tab on wlan service) with Oportunistic Key and Pre-Auth. This option imroved my reconectinos and reconnections on clients.
I dont know really what is the problem, but my clients are going to kill me if the problems persits.
All the changes are made in our floor, only in 4 aps, and when the tests are ok we apply in all the infraestructure.