ASUS RT-AC66U_B1 - Can't get into rescue mode

mkerost

New Around Here
Hi SMB folks. I am unable to get my AC66U_B1 into rescue mode in order to flash non-ASUS Firmware. I've run out of ideas of what I could be doing wrong!

I bought the router in used condition a week ago on ebay. White sticker on back says "HW Ver. B2" and "production year 2020". Text imprinted on the back says it's model B1 though. It boots up and works fine with the supplied ASUS firmware (3.0.0.4.386_49703).

Official ASUS instructions to enter rescue mode are: "While pressing reset button, plug in AC power cord into back of unit, hold reset button until power LED slowly flashes and then release."

However, it never flashes. The LED remains solid. After holding down for a minute, the power LED turns off and the unit remains unresponsive until I reboot it again (whereupon it boots up fine into the ASUS firmware).

From what I've read it should go into rescue mode after 5-10 seconds, however I've held the reset button for as long as a couple of minutes in different tests I've done.

I read that the WPS and reset buttons can sometimes get mixed up. My testing shows holding the WPS down causes the power LED to rapidly blink after 20-30 seconds. I release the WPS button and it immediately reboots with the NVRAM cleared. This is apparently expected behavior. This also allowed me to test attempting to get into rescue mode before/after doing a NVRAM reset, with no difference.

The reset button seems to be functioning. When the unit is running normally, holding it down for 5 seconds causes the device to reboot.

There was a ASUS firmware update available in the web panel. I updated to that (49703, forgot what the old version was called). But it didn't make a difference (either before or after update).

I tried to see if maybe the unit does get into rescue mode but the power LED just doesn't flash. However, after setting my computer, connected to LAN port 1, to 192.168.1.10, 192.168.1.1 doesn't ping and the ASUS firmware restoration utility after 30 seconds says unit is not in rescue mode. Made sure computer didn't have another adapter enabled, etc.

Doesn't make a difference whether I try by holding reset button and plugging in power cord, or pressing power button instead, or holding reset button 5 seconds before powering on, or pressing simultaneously while powering on, etc.

Doesn't make a difference if I leave ethernet cables plugged in, or unplugged, when turning unit on.

I couldn't find any mention that the firmware or hardware of this router would disallow rescue mode. Everything I've read suggests the unit should be able to get into rescue mode.

So that's it... everything I can think of. My next plan of action is to return and try new hardware.

Any thoughts before I return it would be appreciated!
 

ColinTaylor

Part of the Furniture
I've found that it can be finicky trying to get the router into recovery mode. If you're too early or too late releasing the reset button it won't work. I've found that the best method is to setup your PC with its static IP address beforehand and then start a continuous ping running (Windows: ping -t 192.168.1.1). Then try the recovery procedure. IIRC when the TTL changes from 64 to 100 it's time to release the reset button.

What non-Asus firmware are you trying to install? It's possible that if it's not asuswrt-Merlin that it will be rejected.
 
Last edited:

mkerost

New Around Here
I've found that it can be finicky trying to get the router into recovery mode. If you're too early or too late releasing the reset button it won't work. I've found that the best method is to setup your PC with its static IP address beforehand and then start a continuous ping running (Windows: ping -t 192.168.1.1). Then try the recovery procedure. IIRC when the TTL changes from 64 to 100 it's time to release the reset button.

What non-Asus firmware are you trying to install? It's possible that if it's not asuswrt-Merlin that it will be rejected.

Thanks for your help. You were able to put me on the right track and I was able to get it working with FreshTomato.

By having my window ping 192.168.1.1 continually, I could see that it started pinging back a few seconds after turning it on with the reset button held down. I got misled here because the power LED does not "flash" when it goes into rescue mode. The light stays solid for a minute, goes off, then turns solid after another minute, repeats. This is hardly "flashing".

Onto the 2nd issue. I was using the ASUS Firmware Restoration tool to upload the firmware. This is what a number of guides I first stumbled on told me to do. With the ping going on in the background, I attempted to upload firmware with the tool, and noticed the pinging stopped seconds later. The tool was connecting to the device, but doing something very bad and making the device reboot. (I had tried both Tomato firmware and a slightly older ASUS firmware). I got misled here because the tool's error message is: "the device is not in rescue mode". No... it was in rescue mode but the tool broke it somehow.

Seeing that the tool wasn't working, I learned that I can just go to http://192.168.1.1 and use the CFE MiniWeb server to upload the firmware. I used that to upload FreshTomato. I rebooted, and got put into the CFE server again. I cleared NVRAM this time, and booted again. FreshTomato loaded up and I was good to go.
 

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