While trying to use a VPN connection on my Ubuntu server, I found out that when launching my OpenVPN client with :
sudo openvpn --config someplace.ovpn
it makes all my remote services unavailable : my TS3 server, my plex server, my qbittorrent webui and some other minor stuff. Of course I can reach them from within my network with 192.168.X.X:someport, but not from outside with my outside.ddns.net:someport.
I realized after trying to resolve the issue, that my noip client was updating the ddns from myisp IP to the VPN IP, but even if I disable the noip client and ensure that the X.ddns.net stays on my ISP ip, my services are not reachable.
What I would like to know is how to configure my server, vpn service, ddns, ... to have access to my plex server with X.ddns.net:plexport, my torrent webui with X.ddns.net:qbtport, etc ... while using the VPN service. Or if it's not possible, how to only use some traffic through the VPN (for example plex and TS3 server don't go through VPN, qbittorrent yes).
I've read a lot of stuff with iptables and what not, but I've never found a clear and easy answer. I can understand that if all traffic directed at X.ddns.net arrives at my VPN IP, their server while not know what to do with some request to port 32400 which is default for plex media server. What I don't understand is why it doesn't work when I have the X.ddns.net point to my ISP IP, meaning it gets to my router which has everything to route those requests (port forwarding).