Firewalla DHCP mode creates an overlay network above your main network, so if you want to create a port forwarding for your devices, such as accessing your NAS or cameras outside your home, you are required to take extra step to create port mapping on Firewalla in additional to create port forwarding on your router.
For example: If you want to access your home camera's website (http, TCP port 80) remotely, you need to setup port forwarding (e.g. TCP 8080 -> 8081) on your router and setup port forwarding (e.g. TCP 8081 -> 80) on Firewalla. You will be able to access camera website by http://<Firewalla_DDNS>:8080
*Note: For port 8080 and 8081, you can choose your own port, as long as they are consistent between router and Firewalla. It is not recommended to open any well-known ports on your router (e.g. 22, 80, 443 and etc), because it will much more likely be attacked.
Step 1: On your router, create a port forwarding to forward TCP port 8080 to a Firewalla's Port, say Port 8081. Detail step depends on each router's interface.
Here is a general guide: http://www.noip.com/support/knowledgebase/general-port-forwarding-guide/
*Note: If you have multiple layers of routers at your home, you need to setup port forwarding on both routers.
Step 2: On Firewalla, find the Camera you want to access in "Devices", tap "Port Mappings" -> "+" to create a new port mapping. Set the External Port to 8081, as the port on Firewalla; Internal Port to 80, as the Port on your Camera. Tap "Save" to save your setting.
To Access the port: For example, use a browser to access http://<Firewalla_DDNS>:8080. You can find the ddns info in "DDNS" feature, and Your Firewalla DDNS will be automatically point to your public IP.