My setup is described in the image above. I have a raspberry pi connected to a router via Wi-Fi and the router is connected to a host via a Ethernet cable. The router doesn't have a internet connection -- only internal routing - LAN.
So my question is -- how would I set a simple VPN tunnel on the Raspberry Pi which would be used to route all the incoming and outgoing LAN traffic?
I've looked into PiVPN but that requires an Internet connection and I've also looked into PIA's solution to this, but again, it requires an Internet connection. Other guides for LAN only configurations for VPN tunneling haven't been helpful.
Thanks for any help.
EDIT 8:15 PM - 1/8/19: The host is a Programmable Logic Controller (PLC) which is programmed using Ladder Logic. The purpose of this tunnel would be to encrypt the traffic to and from the raspberry pi. In this way another host inside the LAN e.g. attacker computer, wouldn't be able to sniff or modify the data packets send between the two parties.