The provided WiFi Router implements a very restricted DHCP service as follows:
1. It cannot be disabled (this means that I cannot use another device on my home network as a DHCP server)
2. It does not allow addresses to be reserved for networked devices based on their MAC Address.
3. As a result of points #1 and #2 the Port Forwarding provided is strictly limited to devices that are always switched on or are manually configured to have a static address which is outside of the DHCP range.
My suggestion is to update routers to provide a 'more complete' DHCP service that addresses the above limitations.