Select Clients Dropping Wireless Connection On 5500 WLC

[HoustonW]

Recently, my system bought around 800 of the Lenovo Gen 4 Chromebooks. We already had around 2500 Gen 3 100e's that worked perfectly fine, still do. We divided the new laptops out to the locations, and 2 of the 10 locations are having issues where the laptop will disconnect from the WIFI (As in every new device drops off the WIFI within 30-45 minutes of using). We have two controllers, one 5500 for the two locations in question, and a 5520 for the other eight. The other eight locations have given us no grief. Which makes me think it could have something to do with the 5500. The only issue is, I'm not sure where to start looking. Any help would be appreciated.

We have a mix of AP's at the locations. At one location we have 1832 AP's with 1702 AP's, at the other newer location we have 9100 series AP's.

[Leo Laohoo]

(I am not even going to waste anyone's time in asking "what firmware is the controller".)

Reboot the APs and try again.

[HoustonW]

I was incorrect the WLC in question is a 5520 and it is running 8.10.130.0

The AP's have been rebooted, issue persists.

[Leo Laohoo]

Wait a second ... How are they connected to the wireless, Dot1x or PSK?

[HoustonW]

PSK

[Leo Laohoo]

We have a small fleet of about 25k ChromeBooks.  I know, for a fact, that there is a CB OS bug affecting that would cause the OS to disconnect to the wireless.  If the CB authenticate using Dot1X, the CB would very often disconnect/reconnect to the WiFi and it is very obvious when it happens. 

However, if the CB is on PSK, the event does not happen as much but it does happen.  

We reported this issue back in 2021 to Google.  Google finally acknowledged the issue back in mid-2022 and has been unable/unwilling to fix the bug.  

Google is unwilling to share their Bug ID with us.  

[HoustonW]

We have a ticket in with Lenovo and Google as well. We sent logs three weeks ago and it seems like Google has been unresponsive for the most part. That does not seem promising...

[marce1000]

 - Debug clients according to https://www.cisco.com/c/en/us/support/docs/wireless/aironet-1200-series/100260-wlc-debug-client.html  you can have debugs analyzed with Wireless Debug Analyzer

 - Check WLAN timeout settings according to https://www.cisco.com/c/en/us/td/docs/wireless/controller/8-5/config-guide/b_cg85/wlan_timeouts.html

 - For the 5508 controllers , according to https://www.cisco.com/c/en/us/support/docs/wireless/wireless-lan-controller-software/200046-tac-recommended-aireos.html
   go for 8.5.182.11. 

 - Review the 5508 controller configuration according to  WirelessAnalyzer input (procedure) for AireOs controllers
   and feed the output from that into Wireless Config Analyzer

 M.

[HoustonW]

I will look into this. Thanks!

[Rich R]

So you first said the problem WLC is 5500 - there is no 5500 model.  Then you've said it's a 5520 - so at least we're working with an actual WLC model now.  You've said software version 8.10.130.0 which is very old.  Refer to TAC recommended link below - currently 8.10.190.0.

What version is the other 5520 running?

Have you compared the WLC configs line by line for any differences?

[HoustonW]

The controller that is having issues is a 5520 running 8.10.130.0, the other non problematic WLC is a 5508 running 8.5.182.0.

[Rich R · Accepted solution]

Ok then step 1 is upgrading 5520 to 8.10.190.0 to eliminate hundreds of known bugs in that old code.

5508 should ideally be running 8.5.182.11 (link below) to resolve bugs and security vulnerabilities but if it's working you might be happy to stick with 8.5.182.0.

And my question remains: Have you compared the WLC configs line by line for any differences on the relevant WLANs, AP groups etc?

Also 8.10 supports new features not supported by 8.5 - some enabled by default.  You might want to consider disabling those features if they cause issues for your clients.  Also 8.10 with 91xx APs supports WiFi 6 (802.11ax).  Many clients with older drivers have compatibility issues with WiFi 6 so make sure the client OS and drivers are fully up to date.

[HoustonW]

I will be upgrading this this afternoon. When upgrading the WLC is there anything to look out for. I have already grabbed the backup aes file. Is it normal for the file size to be relatively small (87 KB)?

I have looked through the run-config, nothing stood out. I am going to get someone else that knows more than me to take a second look at it.

[Rich R]

Yes config can be quite compact.

Always refer to the release notes for any warnings/caveats:
https://www.cisco.com/c/en/us/td/docs/wireless/controller/release/notes/crn810mr10.html
And
https://www.cisco.com/c/en/us/support/docs/wireless/wireless-lan-controller-software/200046-tac-recommended-aireos.html

Use:
config paging disable
show run-config startup-commands
to get the plain text config from both WLCs and then compare side by side for differences.

[HoustonW]

We have now updated to 8.10.190.0 on the 5520. We are now running into an issue where the 1702i AP's are not wanting to get out of the download loop. All the other AP's have downloaded and are working fine. I have set the date back to may of 2021. Is there another time I should set it?