D-Link DIR-890L User Manual page 151

Section 6 - Troubleshooting
3. Can I connect the DIR-890L to an existing router?
We recommend that you replace your existing router with the DIR-890L instead of using both. If your modem is a combo router,
you may want to contact your ISP or review the manufacturer's user guide so you can put the combo router into Bridge mode,
which will turn off the device's NAT functions.
If you are using the DIR-890L in Bridge mode, and you need to connect it to a router, connect an Ethernet cable from the LAN
port on your router to the WAN port on the DIR-890L. Restart the device and configure the settings. When you have completed the
configuration of the DIR-890L, you can remove the Ethernet cable and move the device to the desired location.
D-Link DIR-890L User Manual 146