Comment 7 for bug 1717995

I'm experiencing this same issue.

A workaround that works for me is to remove my vpn domain from /etc/resolv.conf. The last line of this file looks as follows after a successful VPN connection:

search Home myvpndomain

where the last term is the domain of my vpn (vpn.bla.com). The workaround is to remove it and leave:
search Home
then restart the network-manager service and the VPN reconnects.

Otherwise I have to restart the computer to be able to connect to the VPN after a successful connection. I mean: after a computer restart, VPN always connects, but if I disconnect I cannot reconnect to the VPN unless I restart the computer or do the workaround.

I have a big confusion on how /etc/resolv.conf is managed nowadays in Ubuntu. I have at least three different system processes generating a resolv.conf.

systemd-resolved:
/run/systemd/resolve/resolv.conf

network-manager:
/run/NetworkManager/resolv.conf

and resolvconf:
/run/resolvconf/resolv.conf

My actual /etc/resolv.conf is a symbolic link to this last one. At some point I tried to have only network-manager manage /etc/resolv.conf. Everything works fine, but when I connect to VPN it can't resolve any DNS outside of the private network.

The resolv.conf generated by systemd-resolved has the same problem as the one generated by resolvconf, when the VPN reconnects the VPN domain is not removed from the "search" line.