[arch-general] systemd-networkd and netctl with multiple interfaces

Leonid 'Beef Marsala' Isaev leonid.isaev at jila.colorado.edu
Thu Nov 12 18:20:07 UTC 2015

On Thu, Nov 12, 2015 at 12:30:36PM +0100, Bennett Piater wrote:
> > Say you start out on wifi, and open an ssh connection. Then you plug in
> > ethernet. The ssh session will remain on the wifi route until it is
> > closed. There's no way* to make an existing connection "jump ship" from
> > one route to another. If you were to disable the wifi connection as soon
> > as the ethernet connection, your ssh session would die.
> Thanks a lot, that is both new and helpful indeed.
> So does this mean that new connections will use the new network, while
> old connections retain theirs?

Well, it depends on whether wlan0 and eth0 are on different networks. If
they are, then the answer is yes, and you are screwed.

If both interfaces get the same ip, then you can maintain persistent
connection. For example, let's assume that you constantly switch between
different interfaces (wlan0 <--> eth0), when you move between buildings on

In the latter case, you can bond wlan0 and eth0 (bond0 := wlan0 + eth0) and use
bond0 in all your networking scripts (but still, wpa_supplicant runs on
physical wlan0). In this case, nothing but the kernel cares what physical
interface carries the traffic. Last time I checked about a year ago,
systemd-networkd had some obscure bug in this situation, so I'm using netctl
that works perfectly. If you need, I can dig out the relevant profiles.

Leonid Isaev
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