I made a digital ocean virtual machine using an ubuntu18.4 based pihole+openvpn image. https://marketplace.digitalocean.com/apps/openvpn-pihole
I configured the inbound rules (allowed ssh, , dns, icmp, and port 1194 for vpn), copied the client cert for the vpn, and it works fine, my mobile can connect to the vpn, and I can see the pihole working with pihole -t as well.
But I can't use the vm as a standalone DNS server. (nslookup did not work from my laptop using this vm as the server). with netstat command on the vm I saw that pihole does not listen on eth0, only on the tun0, (the vpn interface). I reconfigured pihole with pihole -r. Selected eth0 as the listening interface (I was unable to select eth0 and tun0 as well) , and then it worked as a standalone DNS server (nslookup worked), but then the vpn became unusable.
How can I configure pihole to work with openvpn and as a standalone dns server as well?