• If you hold down the reset button at boot time, the original bootloader will show a web interface, where you can flash the unit from. It works for installation and recovery.
• The recovery function provides no Internet access, WiFi or DHCP.
• OpenWrt firmware can be flashed directly using this recovery function when using a OpenWrt …factory.bin firmware file. There is no need to first flash official D-Link firmware.
• Official D-Link documentation of this procedure is rare.
  • A german D-Link documentation for the DIR-600 exists (with the same procedure also applying for other D-Link devices, if the device supports recovery).
  • Inofficial documentation: OpenWrt Wiki for DIR-505
  • D-Link Forum.

1 Store a copy of the OpenWrt firmware (.BIN) on the HDD of a local PC
2 Connect an Ethernet cable between the LAN port on the router and the network port on the local PC
3 Configure the PC with a static IP address other than 192.168.0.1 (e.g. 192.168.0.5)
4 Power down the router
5 Press and hold the reset button on the router for 3 to 5 seconds and re-plug the power without releasing the reset button
6 Continue to hold the reset button until the red power light keeps blinking on and off
7 Open a web browser and enter the following address: http://192.168.0.1/
8 Wait for the 'D-Link Router Recovery Mode' page to load
9 Click the [Choose File] button, select the OpenWrt router firmware stored on the local PC and then press [Upload]
10 After the new OpenWrt firmware has successfully loaded, a 'Success' page will display
11 If the 'Success' page fails to display, then repeat steps 4 through 9