before starting this project, I wanted to ask if it was possible to do so.
In practice, I would like to configure a VPN concentrator, which has as its client and DVR, both a single PC. Maybe the scheme is clear:
DVR<->Routerboard<->internet-VPN<->VPN-Concentrator (Routerboard with static public IP)<->internet-VPN<->PC, smartphone, etc.
In this mode my customers can take control over their videosurveillance without a public IP.