I had to restore the D-Link DIR-300NRU/B7 on the inoperative router, which stopped working after turning off the power at the time of the firmware update. In fact, some other D-Link routers can be restored using the method.
To restore you need:
1) Download the latest firmware file from the official FTP D-Link:
2) Turn off the power of the router, press the “reset” button and continuing to hold it to turn on the power of the router, after 10-20 seconds release the “reset” button, the router will have to switch to a special “Failsafe” mode.
3) Prescribe the IP address manually for the computer, for example 192.168.0.100 and the subnet mask 255.255.255.0
4) Open the link http://192.168.0.1 in any browser, the special “Failsafe UI” interface of the router should open, in which click the “Browse” button and specify the previously downloaded firmware file. Press the “Send” button, the firmware will be downloaded to the router and it will automatically reboot (you must wait about 5 minutes).
After these manipulations, the D-Link DIR-300NRU/B7 router should work as before, you can configure it by opening the web interface http://192.168.0.1