I have a client with locally hosted security cameras. There is a DVR box that has a port open and a 3rd party app you can view the cameras from. Traditionally we have been forwarding the port to the WAN via the router there. Its a restaraunt btw.

When the ISP upgrades the router every few years there's a huge headache trying to get the ports back open and bridging the modem and router blah blah blah. Not only this, even though they are supposed to have a static wan ip, it does change from time to time.

What i would like to do is plug in a raspberry pi on the network and forward the DVR's ports somewhere accessable.

Im thinking of something along the lines of wireguard, but just for a single ip/port that i can tunnel over ngrok. Seems doable but i'm having trouble finding the proper terms to google. Port forwarding generally brings up router config, and tunnelling seems to expect you to be on the device who's ports you wish to access.

Any advice?