Re: NetworkManager: network selection

[Dan Williams <dcbw redhat com>]

On Wed, 2015-06-03 at 08:25 +0200, Pieter Cardoen wrote:
> Thomas
> Thanks for the reply. It made some things clear. It is for my application not acceptable that the 
> NetworkManager just prefers the most recently used network but due to the priority feature, it is possible 
> to prefer the WiFi network over a mobile network. However, debian stable doesn't come with NetworkManager 
> 1.0. I will try to install this version on Debian Jessie.

There are really two kinds of "priority" in NM and they are mostly
independent of each other:

1) connection autoconnect when the device is disconnected, which as
Thomas said can be modified by the 'connection.autoconnect-priority'
property.  This is specific to the device, and all autoconnect decisions
are made independently for that device.

2) which device gets the default route and DNS, which can be modified by
the ip4.route-metric and ip6.route-metric properties.  This allows you
to prefer a specific device for outgoing traffic; so if you want the
WiFi to be preferred when WiFi is connected, then you could set each
WiFi connection's ip4.route-metric property lower (which means "more
preferred") than the WWAN connection's ip4.route-metric property.

Does that make sense?

Dan

> ThanksPieter
>
> > Subject: Re: NetworkManager: network selection
> > From: thaller redhat com
> > To: pieter cardoen hotmail com
> > CC: networkmanager-list gnome org
> > Date: Tue, 2 Jun 2015 21:36:41 +0200
> >
> > On Di, 2015-06-02 at 20:56 +0200, Pieter Cardoen wrote:
> > > I have some questions about how networkmanager selects a network.
> > >
> > > How does the NetworkManager deamon decide which network to use if 
> > > multiple network connections are available?
> >
> > Hi
> >
> > when a device is currently not connected, at various instances
> > autoconnect hits. For example when you plug-in your cable and carrier
> > -detect indicates a link. Or when Wi-Fi scanning indicates new visible
> > networks.
> >
> > So, in that case, NM will search through the non-connected connections
> > and choose a candidate to autoconnect.
> >
> > If there are multiple candidates, the one that was used most recently
> > will be used.
> >
> > > Is it possible to configure preferred networks?
> >
> > Yes. Such a candidate must have the "connection.autoconnect" property
> > set to "yes". This is the default. In nm-applet this is called
> > "Automatically connect to this network when it is available".
> >
> > > Is it possible to configure the NetworkManager to only connect to one 
> > > WiFi network and ignore all other free networks?
> >
> > Yes, set all connection.autoconnect properties of the other connections
> > to "no".
> >
> >
> > Since 1.0, there is also a new property "connection.autoconnect
> > -priority". You can assign there a number, see
> >   nmcli connection show CON-NAME
> >   nmcli connection modify CON-NAME connection.autoconnect-priority 1
> >   man nm-settings
> > If there are multiple autoconnect candidates, those with higher numbers
> > will be preferred.
> > So, you could set the priority of the connection you prefer to "1",
> > leaving all others to their default at 0.
> >
> >
> >
> > Thomas
>                                         
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