5GHz WiFi issues with WRT1200AC running OpenWrt 21.02.x

Hello everyone.

I recently decided to make the switch to OpenWrt 21.02 (and then 21.02.1) for my Linksys WRT1200AC router. After having done so, I have recreated the network configuration from scratch because it couldn't be imported from the previous 19.07.7 install.
Since then I experience issues with all devices which connect to the 5GHz band of the WiFi AP (please note that 2.4G and 5G use two different SSIDs). The connection is established but after a while (some hours) the device cannot access Internet any more, even if the link is still marked active; same behavior noticed on Android and iOS devices.
I disabled WPA3 after having read some people reporting instability, but nothing changed.

Before the upgrade to 21.02, everything went fine with the 19.07.7 release.
Interesting fact: my iRobot Braava Jet m6 house cleaning robot can't connect to WiFi at all while using my 21.02 setup, whatever 2.4G or 5G is chosen.
Switching back to my 19.07.7 setup, everything works OK: the Braava robot can connect and the connection is stable for all the connected devices (2.4G & 5G).

I remember that I had some similar problems with versions of the 19.x branch prior to 19.07.7. Is there some recent fix in 19.x that hasn't been backported to 21.x?
I've also found some related topics on the forum but none of them really match what I'm experiencing:

Also, someone reports an issue with 21-rc1 that is new compared to 19.x on a WRT3200 router (https://www.bountysource.com/issues/99322104-anybody-having-issues-since-openwrt-v21-rc1-on-linksys-wrt-3200acm-wrt32x-with-wifi). Don't know if it's related...

Does anyone have a clue on what's going on? :roll_eyes:

Did you try disabling AMSDU?

Thanks for the tip @mortac8. WRT1200AC indeed uses the 88W8864 radio chip.
I've just setup my router with the configuration you propose. I'll report back here the results on the long run.

If it works, would it confirm that this is a mwlwifi firmware issue?
There is a known issue with WRT32xx which seems very closely related; downgrading the mwlwifi firmware may be an acceptable fix.

Does anyone know if there will be further development on this topic?

There is, we have published builds if you could check the main post that you linked.

The AMSDU trick doesn't work for me. I still notice some sort of WiFi instability (need to switch my device's WiFi connection Off then On again to restore the connectivity), plus my Braava robot still can't connect to my AP.

Very nice to read that!
But the WRT1200AC is equipped with a 88W8864 chip, which makes this router different to the WRT3200ACM on a hardware point of view. Your custom builds won't work for me, as far as I understand.

You could compile an image for WRT1200AC using the branch. We use wireless drivers from backports-5.7.5 which might also have an effect on this device.

Curses. Nothing is ever easy :slight_smile:

Have you looked at this?

Thanks for sharing.

As I wouldn't get too far from official releases for this production router (I'm not a developer), I prefer to stick to the 19.x branch for the moment. I'll try future 21.x updates when they will be available.

@Just1M Thank you for posting this and you are not only. I have been a long time user of DD-WRT since my original WRT54G. I recently jumped to OpenWRT 20.02.0 & also tried 20.02.1 for my WRT1200AC as I wanted better stability. I have also been trying to figure out why my 5 GHz WiFi devices (android cell phones and windows 10 laptop) were dropping connections and just stating connected with not internet for weeks now. The only workaround I had was to disconnect the WiFi and reconnect, which is very annoying.

Is there a proper way to report this issue as a bug to be fixed in 20.02.X?

In the meantime, I will install 19.07.8 to see if that resolves these issues and report back.

Update: I have been running 19.07.8 with wpad-openssl using 5Ghz AC and 2.4Ghz N with WPA2-PSK/WPA3-SAE Mixed Mode for a week now with no issues.

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In the same boat, had to downgrade back to 19.07.8. Hope issues with 21 can be resolved soon.

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