Users disconnects randomly with yellow exclamation marks

[mina_raouf]

Hello,

I have a deployment of Cisco 2802I access points, WLC is 5520 running software image 8.5.140.0, and I have a problem where some users suddenly got disconnected and got the yellow exclamation mark on the connection status 

This issue affects some users on a random basis where at the same time other users can work properly, the problem  usually is fixed after rebooting the access point, so any idea why this is happening ? or any fix for this 

note: when users were disconnected some are still obtaining  an IP address while others lose their IP connectivity,

the DHCP pool is not utilized and the SSID is using dot1x  authentication with external radius server 

[marce1000]

 - Have a look at the various tools below ; in your case you might be interested in the Wireless debug analyzer.

 https://developer.cisco.com/docs/wireless-troubleshooting-tools/#!wireless-troubleshooting-tools/wireless-troubleshooting-tools

 M.

[pieterh]

as a first step disable power management on the client's wireless interface.

many times the adapter is put in stand-by mode by the client driver when idle and does not recover when traffic resumes.

[patoberli]

Besides the already suggested options, you might want to try to upgrade to the latest 8.5.151.0 release, as it fixes some rare transmission issues, which you might have.
Do you see anything in the clients Event Log or WLC (debug client mac-address) when that happens?