How to forward a port to a connected machine in SoftEther VPN?

Question

VPN

Hi friends! There was a situation of port forwarding to a machine connected via VPN.
To make it clearer, I sketched out a primitive network diagram:

Everything worked exactly until the moment when we decided to wrap all traffic in a VPN. Now for all clients, the external ip address is the address of the server. On an Ubuntu server with SoftEther VPN, a Zyxel router connects to it via L2TP ipsec. How to configure Ubuntu to forward a port to the port of a vpn-connected machine? On Zyxel, the ports are forwarded, everything worked before connecting via vpn.

Answer 1

Hello. Perhaps this will help you?
here