Please see below setup instructions on how to setup Port Forwarding on a ZyXEL Router.
1.) Open a web browser and type in http://192.168.1.1
2.) It will prompt you for the username and password. By default Username: admin Password: 1234
3.) Now Click on the NAT link.
4.)There should be a dot in the SUA Only setting. If this isn't the case, you can not setup port forwarding without making a major change to your network. I wouldn't advise changing this unless you know what you are doing. Alright, if there is a dot in the SUA Only setting, go ahead and click Edit Details.
5.) Now fill in the following info:
Start Port: The port # of your Camera/DVR
End Port: Same as start port
IP Address: The LAN [internal IP address] IP address for your Camera/DVR
6.) When you're finished, click Save near the bottom of the screen to save your changes
7.) Now make sure the port is open with the following open port forwarding checker tool: http://videos.cctvcamerapros.com/check-open-port-forwarding-tool
NOTE: If the port is open you will use the Remote IP Address you get from the open port tool that you used above. However you will need to type it in as follows via web browser http://ipaddress:port number, eg. if your ip address is 188.8.131.52 than it should look like this when you type it into your web browser http://184.108.40.206:8000.