16.04: issues with wireless on MacBook Pro

Nils Kassube kassube at gmx.net
Mon Jul 4 04:49:49 UTC 2016

Paul Smith wrote:
> On Fri, 2016-07-01 at 07:28 +0200, Nils Kassube wrote:
> > > If I run iwevent I can see a message "Scan request completed"
> > > exactly
> > > every 2 minutes.  I don't know if that's normal or not.  No other
> > > messages are shown.  dmesg shows no messages since I booted.
> > 
> > That looks to me like network manager scans for other networks every
> > two  minutes. As you have an a/b/g/n wireless card, it will scan
> > all available channels on the 2 GHz and on the 5 GHz bands which
> > takes quite some time. On my machine with an a/b/g/n card a scan
> > takes ~14 seconds with only 4 access points visible. And during
> > this time it doesn't transfer the data you're intersted in.
> > 
> > That was the reason why I abandoned network manager many years ago
> > - especially video chat with ekiga was unacceptable with regular
> > sound drops. Since then I use wicd on all machines and never had
> > such a problem again.
> Thanks for this note.  It put me on the right track, and I was able to
> find a solution using Network Manager.  Apparently if you configure
> the wireless connection with the specific MAC address of your
> wireless access point in the BSSID field, then Network Manager won't
> look for "better" connections.

That's interesting - I think I have to try that option and see if it 
works for me as well.

> I still see the scan requests going by every 2 minutes but it doesn't
> seem to interrupt my network access.  I would like an option to force
> scanning off altogether: 99.9% of the time when I use my laptop I
> actually _don't_ want to roam and I know exactly which network I want
> to connect to.  But, as long as it doesn't interrupt my work it
> doesn't bother me much.

The option to disable scanning while connected would be great, and I 
suppose that is the usual situation for many users.

> It appears this is something of a
> contentious issue in the Network Manager world, unfortunately.  The
> author(s) refuse to allow this configuration option and insist that
> if wifi drivers were written correctly it would not be necessary.
>  However this doesn't help people like me who have no choice
> (company-provided hardware) but to use proprietary wireless drivers
> which apparently aren't written correctly.

That was my impression as well and therefore I switched to wicd.

> I want to use Network Manager because (a) it's built in and easy, and
> (b) I need to use various VPNs, and wicd (from what I can tell)
> doesn't support this yet.

Right, wicd doesn't have that many features like network manager, but 
actually I don't need them. OTOH I would prefer network manager anyway 
because it is the standard tool coming with the system.


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