I have the solution for this... I was dealing with a DVR and had the same issue.
The answer was in the pdf version of the user's manual.
Connect to Another Router
If you are connecting the D-Link router to another router to use as a wireless
access point and/or switch, you will have
to do the following before connecting the router to your network:
• Disable UPnPTM
• Disable DHCP
• Change the LAN IP address to an available address on your network. The LAN
ports on the router cannot
accept a DHCP address from your other router.
To connect to another router, please follow the steps below:
1. Plug the power into the router. Connect one of your computers to the
router (LAN port) using an Ethernet cable.
Make sure your IP address on the computer is 192.168.0.xxx (where xxx is
between 2 and 254). Please see the
Networking Basics section for more information. If you need to change the
settings, write down your existing settings
before making any changes. In most cases, your computer should be set to
receive an IP address automatically in
which case you will not have to do anything to your computer.
2. Open a web browser and enter http://192.168.0.1 and press Enter. When the
login window appears, set the user
name to admin and leave the password box empty. Click OK to continue.
3. Click on Advanced and then click Advanced Network. Uncheck the Enable
UPnP checkbox. Click Save Settings
to continue.
4. Click Setup and then click Network Settings. Uncheck the Enable DHCP
Server server checkbox. Click Save
Settings to continue.
5. Under Router Settings, enter an available IP address and the subnet mask
of your network. Click Save Settings to
save your settings. Use this new IP address to access the configuration utility
of the router in the future. Close the
browser and change your computer’s IP settings back to the original values as
in Step 1.
6. Disconnect the Ethernet cable from the router and reconnect your computer
to your network.
7. Connect an Ethernet cable in one of the LAN ports of the router and connect
it to your other router. Do not plug
anything into the WAN port of the D-Link router.
8. You may now use the other three LAN ports to connect other Ethernet
devices and computers. To configure your
wireless network, open a web browser and enter the IP address you assigned to
the router. Refer to the Configuration
and Wireless Security sections for more information on setting up your
wireless network.
Regards!