Linux NetworkManager is a great utility that usually “just works”, yesterday I did however notice that I was not able to access an internal network while using an OpenVPN connection through NetworkManager because the domain names were not resolved as they should (my normal DNS was used instead of the DNS that the openvpn server pushes out).
Finding a solution was not easy and there appears to be no way of manually overriding DNS server either. Eventually I found this bug which has been around for a couple of years and is still not solved.
Fortunately the workaround is simple – you need to disable NetworkManager’s use of DnsMasq. This is done by modifying the configuration file. To modify it you need to open it with a text editor (like gedit) as administrator (sudo). Open a terminal and paste this command (right-click and choose paste – ctrl+v doesn’t work in the terminal):
sudo gedit /etc/NetworkManager/NetworkManager.conf
It will ask you for your password and then open the file so that you can put a # before the dns=dnsmasq line (this means this setting is now disabled) and click save and close the text editor.
Finally you need to restart the network manager (or reboot):
sudo service network-manager restart