I recently got a Asus RT-AC3200 wireless router for a project I’m experimenting with. Naturally, the first thing I did was to flash it with some custom firmware, in this case DD WRT which worked fine but there was a feature missing that I needed. I then wanted to change back to the stock firmware, however trying to use the standard upgrade method didn’t work for some reason. Asus offers a recovery tool via their website but only for windows. But, looking in the forums it turns out that it’s pretty simple to do this manually (and on linux).
First, turn the router off. Then turn it on while holding the reset button for a few seconds. It will then boot up into a recovery mode where you can ping it and send files to it but that’s about all. So, plug your computer in, manually configure your (wired) interface to 192.168.1.2 (I don’t know if this is actually required or not) and run:
$ tftp 192.168.1.1
tftp> mode octet
tftp> put RT-AC3200_380.60_beta2.trx
Sent 43192320 bytes in 125.8 seconds
Then reboot your router and the firmware has been forcibly updated! It’s probably worth to do a ‘factory reset’ after installing any new firmware as the nvram differs between different versions.