Pihole stopped taking requests from LAN after installing OpenVPN

[Vykaax]

Please follow the below template, it will help us to help you!

I've installed Pi-hole in Ubuntu 16.04 on a VM. Configured my EdgeRouter to set all of my subnets to use the Pi-hole server as DNS, opened the traffic between subnets for the Pi-hole server on port 53, enabled DNS forwarding on all of the EdgeRouter interfaces and then confirmed that everything was working properly. After Pi-hole was up and running, I proceeded to install OpenVPN on the same server. The VPN works and I can connect to my network externally, but now within the LAN there is no DNS happening

What I've already tried and confirmed in settings:

• Pi-hole is set to 'listening on all interfaces'
• Pi-hole is NOT setup for DHCP, the EdgeRouter is handling that
• The Pi-hole server IS capable of resolving DNS itself (but I guess this is because it's using the Upstream DNS, right?), I can ping google, update Gravity, etc
• No other services are trying to use port 53, only pihole-FTL
• sudo ss -tlnpax indicates that pihole-FTL is the only thing using port 53
• sudo netstat -tulpn indicates it is listening on TCP port 53, but the state is blank on udp port 53
• Pi-hole's ethernet interface is still correctly set to ens160 rather than tun0
• Manually setting a public DNS (8.8.8.8) on clients brings them back to life, setting it back to auto or manually setting the Pi-hole address as DNS kills them again
• dig pi-hole.net from the Pi-hole server resolves using 127.0.0.1#53
• dig pi-hole.net @piholeip from any client times out with 'no servers could be reached'
• dig pi-hole.net @8.8.8.8 or the gateway resolve

Expected Behaviour:

Pi-hole should receive and resolve DNS requests from all LAN subnets

Actual Behaviour:

After OpenVPN was installed, Pi-hole stopped receiving DNS requests. Client's cannot resolve DNS and the Pi-hole query log now shows only the Pi-hole server itself as of the completion time of the OpenVPN install

Debug Token:

13sufwsste

[HvdW]

I do not know a lot about the ins and outs.
The only thing I do know is that I followed Marc Stan's tutorial and everything is running smooth.

BTW
Just today I had the situation that only one client was connected.
Main page, Top Clients, just localhost.
Debug showed nothing extraordinary.
It took me less than half an hour to uninstall PiHole and unboud, set both up again, check Marc Stan's settings and it running as before.
What I have learned is that it is very rewarding to dive deep into the problems and find out the cause, but that it often more rewarding to just uninstall and install again.
It takes you mostly out of trouble right away.

Hope this helps you.

[Vykaax]

Thanks HvdW.

Will definitely look at that guide the next time around.

For now, it seems I've fixed it after many hours of troubleshooting. It turns out I'm an idiot and put interface=eth0 in my custom dnsmasq conf file, and the interface in my VM is actually ens160. I believe I must have done this at the point between having Pihole working, then following steps to configure OpenVPN and just happened to zone out and add whatever the guide said instead of what my interface actually was which then nuked my internal DNS.

So yeah, lesson learned.

[HvdW]