Re: "Adapter Switching" option which powers down the wireless radio when a wired ethernet connection is detected

[John Walicki <walicki us ibm com>]

Dan Williams <dcbw redhat com> wrote on 09/17/2012 04:32:56 PM:

> On Mon, 2012-09-17 at 14:11 -0400, John Walicki wrote:
> > In the Intel ProSet utility on Windows there is an "Adapter Switching" 

> > option which powers down the wireless radio when a wired ethernet 
> > connection is detected.  The wireless radio is powered down when the 
> > ethernet cable is inserted and the wireless adapter is powered on once 

> > again when the ethernet cable is removed. 
> > 
> > Normally, a dual homed environment with both wired and wireless having 

> > assigned IP addresses is preferable.  Routing will send the packets 
over 
> > the preferred interface.   We're constrained by the available IP range 
for 
> > wireless devices and only want to assign the IP address if the laptop 
is 
> > untethered.
> > 
> > Is this possible with NetworkManager?
> 
> Hi John,
> 
> This was brought up in the last two weeks, and we approached it by using
> Dispatcher scripts to "airplane mode" the wifi.  That should work for
> you if you don't mind a short period of time (like 1 second) where both
> the wired and the wifi networks are connected with IP addresses.  This
> would entail a dispatcher script that:
> 
> 1) whenever it gets an "up" event, runs "nmcli dev" and looks for any
> line that contains *both* "802-3-ethernet" and "connected"; if one is
> found, it executes "nmcli nm wifi off".
> 
> 2) whenever it gets a "down" even, runs "nmcli dev" and looks for any
> line that contains *both* "802-3-ethernet" and [ "connecting" or
> "connected" ].  If none of these lines around found, it runs "nmcli nm
> wifi on".

That approach works for me.  Are there some sample dispatcher scripts that 
we could leverage?
Thanks for the tip.  I had proposed flipping the hard wireless kill switch 
but that requires teaching users to participate in helping the network 
infrastructure.  That rarely works out well.

We have some locations that have so many smart phone/mobile devices 
soaking up wireless IP addresses that we're running out of IP ranges. With 
thousands of Wireless Access Points, we're scaling infrastructure and 
reconfiguring networks as quickly as we can.  Good thing we have a Class 
A.  This might be a safety valve.

> 
> The previous query had a network that simply would not give a DHCP lease
> when the wifi still had an IP, and the dispatcher scripts could not
> handle that case (yet).  However, all that information is available via
> D-Bus, so that's another option.
> 
> That said, this is something that might make sense to integrate into NM
> on a more permanent basis in the future.

Yes, this would be a nice feature to fully integrate into NM.
-- John

> 
> Dan
>