How to build an L2TP tunnel for client access?

Question

CCTV

There is a DVR, a router, a 3g / 4g provider with a gray IP, a VPS with ubuntu and a white IP.
I was puzzled by access to the reg without P2P. For this, I chose L2TP. Why not OpenVPN? Because the router from the box can only L2TP. Encryption is not needed.
I installed xl2tpd on the VPS (why did I find it first). And then the plug. I can't handle the config. And here's what you need:
The router connects to the VPS using a login and password, raises a tunnel. The user accesses the VPS via a white IP and gets to the DVR. Everything seems to be simple.
Then there is the same video recorder in another place2. Do not raise the second VPS. So you need a second white IP2. And turning to him we get already on the video recorder2. This is what it should be.
Tell me what to do with the config, or raise your own tunnel for each DVR, or they will be in 1 tunnel, I don’t understand. And maybe there are other products that will cope with this task?