Succeeded flashing R6400v2 back to stock (Netgear firmware)

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TXUSA
TXUSA's picture
Succeeded flashing R6400v2 back to stock (Netgear firmware)

I finally broke down and opened up my messed up router to give it a fresh start with a stock firmware image. I used a usb-serial cable and then flashed it via TFTP/network cable once I managed to start up the TFTP server on the router. 

The process is generally the same as it is explained in many other internet posts... if you have questions, ask.

Here are some interesting takeaways:

Once I opened the router I saw that there was a board ID printed on there (U12H332T20 which is incorrect), but then discovered a sticker close to it that lists it as U12H332T30 which is correct - and I also got confirmation it is right from the actual output from the serial connection. 

Another annoying caveat... the firmware image that Netgear posted on its own website is literally worthless... that is because the "image ID" (the ID tag that is embedded in the firmware file) is wrong. For a firmware image to be written and stored successfully board ID and image ID have to match. Netgear posted a firmware file on its website that only would work on the 6400v1, as far as I can see. Even though it is listed in the v2 download section. Although it looks like the firmware is being written the changes aren't stored and after a restart the router boots straight back into whatever firmware file was on there previously. How can that be fixed ? Well, it takes downloading a hex editor (I used HxD), downloading the firmware file from the Netgear website, opening it up and changing that one byte that is part of the image ID from a 0 to a 3 and save... so the whole thing then reads U12H332T30 instead of U12H332T00 in order to successfully be written and stored.

I can't confirm if the process works if the stock file is changed with a hex edior and then being flashed through the web GUI... but the two ID tags definitely have to match for this process to work correctly.

 

Subatim
Subatim's picture
Hi, Thanks for this.

Hi, Thanks for this.

I've been suffering for gone a month now. I was looking into your tip of using a serial usb connection and found this tool,  nmrpflash.

https://github.com/jclehner/nmrpflash.

With this I was able to ftfp a Netgear firmware via an Ethernet port. 

 

TXUSA
TXUSA's picture
Wow that is really cool ! I

Wow that is really cool ! I will look into that for sure ! Thanks for sharing Subatim !

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