[masraum]

Originally Posted by Lexus4321

It's because directly to the modem, the modem gave the NVR a public IP address. Once you go to adding the router the modem gives the router a public IP address.

Plug the NVR into the yellow 4-port on router, give NVR a static IP in whatever subnet the router LAN is (192.168.x.y, etc). Then on the router you need to do some port forwarding between it's WAN public interface (which was given a public IP from the modem) to the internal 192.168.x.y static IP. This is the only way to get inbound to map public IP and service port(s) to the internal NVR 192.168.x.y IP address.

OPTION-B - if your provider allows say ten devices (hence the modem will assign 10 IP's via DHCP, then you can easily use a Netgear (or the like) 4-port switch, and then plug it all into the switch. Hence, plug the modem ETH, router WAN port, and NVR into the switch. The modem will give router and NVR a public IP. You can then access the NVR from internet and wifi using the public IP that was given to the NVR. Just make sure you give your NVR a really good password (10 chars, mix of numbers letters and one or two specials like !@#$%^&*() ) , etc

Option-B is the easiest for you if you cant figure out port forwarding on the router.

Exactly. The existing router would probably work for Option B as long as you do NOT use the WAN port. But I'll be surprised if your ISP offers multiple DHCP addresses.