Can surveillance station be used with cameras that are not on the same network as the NAS?

[jeyare]

must correct my wording:
there isn’t problem of connection over WAN between IP camera and NAS.
there is a un shielded RTSP protocol used for such communication, what is totaly vulnerable over WAN.Then Site to site VPN is the best solution for covering.

 

[WST16]

You can access the camera with http or https. Maybe not all of them offer that.
Here’s the port settings on a Hikvision. One can just forward the https port on the router where the camera is on the remote site and ignore the rest.