Ubuntu 16 : "bug hasn't been fixed since 2017 : DNS server from vpn connection has not being used after network-manager upgrade to 1.2.6"

[lsat 23]

https://bugs.launchpad.net/ubuntu/xenial/+source/network-manager/+bug/1688018
More recent versions of Ubuntu seems not to be affected,  but please watch out for your current tests on this issue.

As systemd-resolve --status doesn't work on Ubuntu16,  users can check their situation with journalctl -u systemd-resolved -f
 

Quote

https://unix.stackexchange.com/questions/328131/how-to-troubleshoot-dns-with-systemd-resolved
Very helpful for troubleshooting is also:

journalctl -u systemd-resolved -f

There you can see what systemd-resolved is really doing. In my case it was not contacting the DNS servers that were reported via systemd-resolve --status at all. If it's doing weird things like that, then somtimes a restart via sudo systemctl restart systemd-resolved is a good idea.

EDIT: In order to get more information from resolved you need to put

[Service]
Environment=SYSTEMD_LOG_LEVEL=debug

into the override.conf of systemd-resolved via

sudo systemctl edit systemd-resolved

 -------------------------------

It might be worth noting that after running sudo systemctl edit systemd-resolved it seems sudo systemctl restart systemd-resolved needs to be run in order for the new settings to be applied. Thanks! – bmaupin Apr 23 at 15:13
After all these years without having to deal with windows, not much anyway, you get the "If it's doing weird things like that, then somtimes a restart via.." advice and you know you are back to where you started