Link>
Welcome!- What Hardware version is your router? Look at sticker under router.
- Link>What Firmware version is currently loaded? Found on the routers web page under status.
- What region are you located?
Internet Service Provider and Modem Configurations- Is ISP Modem/Service using Dynamic or Static WAN IP addressing?
- What ISP Modem service link speeds UP and Down do you have?
- Check ISP MTU requirements, Cable is usually 1500, DSL is around 1492 down to 1472. Call the ISP and ask. Link>Checking MTU Values
FW is mainly handled by ISPs only and not by D-Link for the modem. This model model is fairly old now so it may not be supported by the ISP as far as FW goes. You may want to get into a Motorola SB 6 series stand alone modem.
I recommend that you have your ISP check the cabling going to the ISP modem, check signal levels going to the ISP modem. Check the phone lines for correct operation and filtering. The modem is dependent upon getting good signal from the ISP Service.