One way is to use port forwarding. Try setting up an address reservation for the MAC address of the CCTV (use a higher IP number such as 192.168.0.130), after you power cycle the router, the CCTV should be using the IP you set up. Next set up port forwarding so you can assign the IP to specific ports in order to get to the CCTV from the outside internet. The CCTV instructions should show the ports you need to set up. Then set up a DNS service such as NO-IP (you can use the free version). Assign a unique host name. On your remote device, install the app for your CCTV access and use the host name you set up.