FAQ: Oooops I've bricked the router - ntadmin/DGND3700v2 GitHub Wiki

Sometimes a perfectly normal firmware upgrade bricks the router. The upgrade doesn't complete and when you power cycle the machine it just turns the red light on, and nothing else happens. For all of the following options, please use your discretion and, entirely at your risk.

All of this information is quite possibly DGND3700v2 specific, it is very probably Netgear specific. Please don't contact me asking how to do this on other routers. I don't know.

Standard first method to try

With thanks to mvmhk on the whirlpool.net.au forum:

  1. Get a PC with an ethernet connection.
  2. Get a copy of the router firmware you know works, and put it on that PC.
  3. Stop every connection that PC has to any netwrok.
  4. Configure the PC to set the ethernet connection to have IP 192.168.0.10 and netmask 255.255.255.0
  5. Connect the PC, by cable, to the DGND3700v2 (LAN ports)
  6. Start a browser and point it to 192.168.0.1

All being well, a very simple web page will come up inviting you to choose a firmware file and upload it. Follow the instructions on the page. When it comes back up, expect it to have the IP it had before it was bricked, which is probably not on 192.168.0.X, so you will probably need to reconfigure the ethernet port to check it's there and running.

OK, that didn't work, try this

I did this from Windows 10. Things you need:

  1. nmrpflash ready to run on your machine. To do this, follow the instructions here. Don't ignore the note about WinPcap if you are trying to orchestrate the recovery from a Windows PC.
  2. An image file that is known to work. Perhaps wise to switch back to an official Netgear one at this stage. WE'll call it DGND3700v2.img for simplicity here.

For this we will be giving the router a temporary IP of 192.168.1.100. So if you see that IP address, remember to change it for whatever you are using for it for this process. (This address doesn't stick around afterwards, so just pick one on the same network that you know is unused. I used 192.168.1.100 because it is listed as an IP for the machine very early in the boot sequence, before it switches to 192.168.0.1, which itself is used (see above) before it switches to the one you set for it when you configured it ages ago, some time before you bricked it.)

Make a cup of tea, and steady your nerves. Here goes:

  1. Turn off the router.
  2. Connect the WAN ethernet socket to your device, or ethernet 4. But not, in my experience, ethernet 1.
  3. Find out the name of the interface on the rescue machine you are using by calling nmrpflash -L. On my machine it was net1, so I'll use that for the example in the next step.
  4. In rapid succession, issue the following command, with net1 and the image file changed to match yours, and then turn on the router: nmrpflash -i net1 -f DGND3700v2.img -a 192.168.100.
  5. when nmrpflash exits, things are probably good.
  6. Wait for the router light which is orange (the 'world' one I think) to start flashing orange.
  7. Wait until you feel ready for it. The orange light flashing may mean something, but there is no clear concsenus on that out that. In my experience a minute of flashing is fine, but seehere.
  8. When impatience or bravery overcomes sensible caution, power cycle the router.
  9. Bob may, or may not, be the husband of your mother's sister.

Now, it may be that a lot of settings were reset as you sought to bring the router back to life, so it will, quite possibly, be back at 192.168.0.1 ...