In your LAN router/gateway, add a static route along the lines of :
"For network 192.168.254.0/24 (ie subnet mask 255.255.255.0) use <IP_address_of_NVR_LAN_interface> as the gateway"
Ok, I have Motorola NVG589 router. I could not find Static Route. So I searched My model, and found that this Cascaded Router is what I need to change. But I tried several combinations of IP's in the fields, but I would always get some error about an IP in the Network address field. .
See attached photo of the options I have for the Cascaded Router area.