Hi there!

  > I haven’t really investigated if it is possible to do it on demand.

It is, and it's pretty easy. You need to add the following in your 
systemd-networkd .network file:

[Link]
ActivationPolicy=manual

The default being "up", as you've discovered.
See 
https://www.freedesktop.org/software/systemd/man/latest/systemd.network.html 
for more options ("Takes one of "|up|", "|always-up|", "|manual|", 
"|always-down|", "|down|", or "|bound|".")

Hope this helps!

axel

Hi!

>> I haven’t really investigated if it is possible to do it on demand.
> 
> It is, and it's pretty easy. You need to add the following in your 
> systemd-networkd .network file:

Thanks for the feedback, that can definitively be useful. I've added a 
link to your message on the blog too, in case someone else stumbles over 
the post.

Linus