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How to flash RT-N66U with Shibby's TomatoUSB firmware


Download Asus RT-N66U Flash utility

Download Shibby RT-N66U firmware

K26RT-N is appropriate for the RT-N66U. Go ahead and pick the latest release by date. Inside that directory you want the to pick the Asus RT-N66u 64k. The 64k in the name means that 64k of flash memory will be used as NVRAM. Inside that directory the .trx file with AIO in the name has all possible features compiled in and enabled. If this is your first time installing, AIO is a good jumping off point.

Preparing for firmware restoration to TomatoUSB (Shibby)

The steps are simple, you will need to:

  1. Connect the ASUS RT-N66U to your network
  2. Start the firmware restoration process (using firmware restoration utility in the ASUS Utility package) so that it is searching for router
  3. Put the ASUS RT-N66U into firmware restoration mode and start the firmware restoration process

Before you proceed, pull out the power cable to your RT-N66U and have a pen ready to press the reset button (between the USB ports and WAN port)

Flash the TomatoUSB firmware onto the RT-N66U.

  1. Launch the firmware restoration utility (this is one of the tools in the Utility you installed earlier)
  2. In the firmware restoration utility, browse for the TomatoUSB firmware you have downloaded earlier
  3. Start the firmware flashing and a prompt should appear stating that it is an incompatible firmware. Proceed to the next step.

Putting the RT-N66U into emergency firmware restore mode

  1. Press and hold on to the reset button
  2. While holding down the reset button, plug in the power cable so that the RT-N66U turns on. Note: Keep holding the reset button until the power led starts to flash (on and off). When power led starts flashing, release the reset button and proceed.
  3. On the firmware restoration utility, agree to the prompt saying that it is a incompatible firmware. The utility should be scanning for device. Proceed to the next step
  4. Wait until the flashing is complete
  5. The router will automatically power cycle when it is complete

Finally, clearing the NVRAM before you use TomatoUSB

It is always a good practice to clear out the previous settings (in NVRAM) whenever you flash to different firmwares. This is true for PC BIOSs as well. In this case, it is required to flush out the NVRAM from values that may have been previously stored by the stock firmware that are no longer valid for TomatoUSB.

You can either flush the NVRAM either through key presses or through web admin.

Clearing NVRAM via key presses

  1. Power off the RT-N66U
  2. Press and hold down the WPS button
  3. While holding the WPS button, plug in the power cable to turn RT-N66U on
  4. Keep holding the WPS button for 30 seconds before releasing The router should reboot
  5. Congratulations. The NVRAM has been cleared.

Clearing NVRAM via web admin

The TomatoUSB administration web should be at If it is not, do a “ipconfig” or “ifconfig” and navigate to the gateway address with your web browser. If you are not able to get an IP address from DHCP, you might want to set your computer’s IP address to

When prompted for a login, the default is:

  • User: root
  • Pass: admin

Once you are in, follow the next step to clear out the previous settings

  1. Navigate to Administration -> Configuration
  2. Under Restore Default Configuration, select “Erase all data in NVRAM memory (thorough)
  3. Click “OK”
  4. Wait for the router to be ready
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cpryor6 commented Jul 19, 2016

I have one of the older units marked B1 and ran into the reboot loop after not getting the webui up fast enough and having the upload fail partway through. I was able to recover it by clearing NVRAM which gave me the default ASUS login page as if it was brand new out of the box. I was quicker with the webui next time and got the 9MB VPN version installed in like 15 minutes. Thanks to the OP and contributors for this writeup.

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For Mac OSX users, ASUS has an app in the Mac App Store called "ASUS Firmware Restoration". I just used it to flash my RT-N66U with Tomato on my MacBook and it was easy.

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netrbrunet commented Jul 28, 2016

Thank you to all' this was great. And extra credit to docbill for the simplified version.

Note, my new N66U's disk did not come with the recovery utility, and I had to download it from ASUS site. At first, I was trying to upload tomato via the default firmware's updater but this is not the same as the specialized firmware recovery utility.
However, I should note that it never gave me an error (maybe a newer version of the updater?). It uploaded the file (a short progress bar), and then started a subsequent "system recovery in progress" progress bar which took about 5-10 minutes to complete.

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morgant commented Sep 9, 2016

I just did this from a Mac and found the process to be very unreliable. I ultimately got it to work with a combination of @docbill's & @AaronCompNetSys's instructions, plus the note I found in Googling regarding watching for whether the antenna lights were active or not, that really helped).

  1. Erase the NVRAM (because of failed flashing attempts, it was trashed anyway; you might move this step to the end or skip entirely if you're wiping the NVRAM via Tomato's web interface)
    1. Turn off router
    2. Hold down the WPS button
    3. Press the power button to turn the router back on (the power light will flash quickly)
    4. Continue holding down the WPS button for a full 30 seconds, then release
    5. The router will reboot
  2. Flash the firmware using ASUS Mini Web:
    1. Set your Mac/PC to static IP in range (I used (IP), (subnet mask), and (gateway))
    2. Turn off router
    3. Unplug router
    4. Hold down the reset button
    5. Plug the router back in
      6 Press the power button (the power light should blink slowly—2s on, 2s off)
    6. Load in the browser on your Mac/PC
    7. Quickly select the firmware you want to use (MIPSR2-138-Mega-VPN didn’t work for me, but MIPSR2-137-Mega-VPN did)
    8. Click ‘Upload’
    9. AS SOON as the “Received file” message loads in your browser, LET GO OF THE RESET BUTTON!
    10. The power light on the router should go off (if it doesn’t, it didn’t work… maybe not fast enough selecting the firmware, maybe a poorly timed release of the reset button… go back to the beginning and try again.)
    11. Wait for 5+ minutes for the firmware to process/install (the power & antenna lights will remain off for this entire time, though the ethernet light for the port you’re plugged into should stay on)
    12. Once successfully installed, the router should reboot (power light will come back on, then the two antenna lights.. if this doesn’t happen, esp. the antenna lights, something didn’t work… I’d suggest trying a slightly older firmware version)
    13. Give it another minute or so and then load in the browser of you Mac/PC
    14. Log in with the default username/password of “root”/“admin”
    15. If the NVRAM wasn’t successfully cleared, do so now (either manually as described above or through your new firmware).

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I was having real trouble getting larger images to flash at all, either through the recovery app, the web UI, or TFTP. I ended up searching for the smallest image I could find, and used tomato-K26-1.28.RT-N5x-MIPSR2-120-MiniVPN.trx. From there, I could flash a recent all-in-one image.

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Process that worked for me on a Mac:

  • Install the asus device discovery and firmware flash utils from app store
  • Reset NVRAM (not sure if necessary, but why not) using steps above
  • Put it into emergency firmware restore mode (otherwise the upload craps out at about 25%) using steps above
  • Upload a small tomato firmware, I just used because @deviantintegral recommended it. This is because the finicky part of this process seems to be going from Asus -> tomato.
  • Reset it manually (toggle switch on and off)
  • Wait for a new DHCP address (about 30 seconds)
  • Installed a fully featured, recent all-in-one image, checking the "clear NVRAM on reboot" setting so that it automatically clears the NVRAM again. This takes a few minutes to upload and reboot, and will reboot a couple of times, but the Web UI is very informative on the progress.
  • Confirm the new firmware version
  • Enjoy my new, recent, tomato firmware.

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Double check the version of your router. I've spent some time following the instruction here without success. Finally I've double checked and it seems ASUS released a "B1" hardware version of RT-AC66U, which is not compatible with all previous generation firmwares for RT-AC66U (A1).

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@tomaszkoperski: Do you know if there's a tomato-shibby (or AdvancedTomato) version that is compatible with the RT-AC66U_B1 hardware revision?

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Is there any newer Tomato than from 2015? The file I am looking at doesn't have the same naming schematic as the one to poster says...

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Trefilov22 commented Apr 21, 2017

And why couldn't you use the firmware update option from inside the Router? I only ask this because my laptop doesn't have an ethernet port to connect directly to the router, I pretty much have to do everything thru WiFi...

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kikiSK commented May 14, 2017

I ask for help.
How to connect Asus VDSL AC68U / main router / and Asus RT N66U Tomato 1.28 shibby I think Lan to WAN port

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I have the RT-66R router, will this firmware work on this one too?

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quangv commented Oct 26, 2017

anybody have a mirror of this? is down for me

edit: yeup, it's back

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stullekovski commented Oct 29, 2017

Looking for the same as @quangv. is still down.
Especially for versions before 138 MultiWAN for my RT-N66U. Thanks a lot!

Edit: it's back online.

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Thanks @docbill @AaronCompNetSys, excellent instructions. Anyone else who arrives here: take what people are saying about loooooong reboot time seriously. For me it was like 20 minutes after seeing "Failed to connect to the wireless router. Check if the router's power LED is blinking, which denotes rescue mode".

Finding the smallest possible Tomato firmware to initially install, and then installing your desired one from there, sounds like the way to go; that's what I would try if I (shudder) had to do this again.

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saulp commented Mar 30, 2019


Skip the instructions in the original post. Read docbill's and AaronCompNetSys' instructions first.

Especially the second link, with the process to simply skip the unnecessary and frankly crappy Asus software:

1. docbill

2. AaronCompNetSys

(thank you both!)

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What worked for me was to flash the DD-WRT firmware from the console administration web console, then flash the shibby firmware from the DD-WRT admin web console.

This is so much easier lol. Idk why anyone is doing it any other way. Fk that.

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