Re: wifi permanently switching between 2.4 and 5 GHz

[Dan Williams <dcbw redhat com>]

On Tue, 2018-08-14 at 23:04 -0500, Greg Oliver via networkmanager-list
wrote:
> On Tue, Aug 14, 2018 at 2:24 PM "Jürgen Bausa" <Juergen Bausa web de>
> wrote:
>
> > I have a Xiaomi Air 12 Laptop (Intel Core m3-7Y30, Network
> > controller:
> > Intel Corporation Wireless 8260
> > (rev 3a)). I use debian Stretch (linux 4.9.0-7-amd64) with KDE and
> > Network-Mananger (1.6.2-3).

This is behavior specific to wpa_supplicant and how it decides to roam
between access points.  It attempts to roam to a BSSID within the same
SSID that has a better speed/signal.  It is expected that it might jump
between BSSIDs when conditions change.

Does the switching cause an actual problem?  It's supposed to happen
very quickly, within a couple 10s of ms.

Dan

> > Until now, wifi worked fine. However, after I exchanged my router
> > (which
> > had only 2.4 GHz) against a
> > newer model that has both 2.4 and 5 GHz (both frequencies with the
> > same
> > ssid), I experienced the
> > following problem: The computer switches permanently between both
> > frequencies. This happens approximately
> > every 2 minutes. In /var/log/messages I find the following:
> >
> > Aug 12 14:45:12 lina kernel: [ 2256.208621] wlp1s0: disconnect from
> > AP
> > xx:xx:xx:xx:xx:xx for new auth to yy:yy:yy:yy:yy:yy
> > Aug 12 14:45:12 lina kernel: [ 2256.213032] wlp1s0: authenticate
> > with
> > yy:yy:yy:yy:yy:yy
> > Aug 12 14:45:12 lina kernel: [ 2256.223163] wlp1s0: send auth to
> > yy:yy:yy:yy:yy:yy (try 1/3)
> > Aug 12 14:45:12 lina NetworkManager[564]: <info>  [1534077912.6843]
> > device
> > (wlp1s0): supplicant interface state: completed -> authenticating
> > Aug 12 14:45:12 lina kernel: [ 2256.228342] wlp1s0: authenticated
> > Aug 12 14:45:12 lina kernel: [ 2256.229481] wlp1s0: associate with
> > yy:yy:yy:yy:yy:yy (try 1/3)
> > Aug 12 14:45:12 lina kernel: [ 2256.230627] wlp1s0: RX AssocResp
> > from
> > yy:yy:yy:yy:yy:yy (capab=0x11 status=0 aid=1)
> > Aug 12 14:45:12 lina kernel: [ 2256.231932] wlp1s0: associated
> > Aug 12 14:45:12 lina NetworkManager[564]: <info>  [1534077912.6931]
> > device
> > (wlp1s0): supplicant interface state: authenticating -> associated
> > Aug 12 14:45:12 lina NetworkManager[564]: <info>  [1534077912.7338]
> > device
> > (wlp1s0): supplicant interface state: associated -> 4-way handshake
> > Aug 12 14:45:12 lina NetworkManager[564]: <info>  [1534077912.7414]
> > device
> > (wlp1s0): supplicant interface state: 4-way handshake -> completed
> >
> > where xx:xx:xx:xx:xx:xx the MAC of 2.4 and yy:yy:yy:yy:yy:yy the
> > MAC of 5
> > GHz net is.
> >
> > However, this happens not at all places in my house. Near the
> > router, 5
> > GHz is much stronger than 2.4 Ghz
> > and the system keeps th 5 GHz net. But in the living room, both
> > nets have
> > nearly the same strength and the
> > systems switches all the time.
> >
> > I found a lot of description of exactly this problem, but no
> > solution on
> > the net. See e.g.
> > https://forum.manjaro.org/t/frequent-wifi-disconnect/12211
> >
> > https://jeremyfelt.com/2017/01/02/things-i-learned-or-broke-while-t
> > rying-to-fix-my-wireless-in-ubuntu-16-10/
> >
> > https://www.archybold.com/blog/post/intermittent-connectionhigh-pac
> > ket-loss-intel-wireless-driver-iwlwifi-ubuntu-linux-networkmanager
> >
> > I think there should be some treshold that avoids switching between
> > nets
> > based on small fluctiations. But
> > where can I set this treshold. And is the switching caused by NM or
> > by the
> > driver? As the bugreports
> > mention different adapters, I think its not driver specific.
> >
> > Any hints welcome.
> >
> > juergen
> >
> > This is a long time nuisance of mine with NM and wpa-supplicant in
> > Linux.
>
> I just set the BSSID in NM to the MAC of the 5Ghz chip on the AP
> .  This also keeps it from scanning into 2.4 and causing 10 seconds
> drop
> outs.
>
> Unfortunately, I do not think a better way exists in Linux, which is
> unfortunate for us desktop users.  IMO, it is a major flaw that needs
> to be
> reworked ground up - it only happens on Linux (compared to MacOS and
> Windows on the same AP anyway - I have never run *BSD variants on a
> desktop
> machine).
>
>
> -
> Greg
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