Upgrading ASUS RT-AC66U to TomatoUSB

ASUS RT-AC66U - TomatoUSB (Shibby) on the ASUS RT-AC66U
ASUS RT-AC66U – TomatoUSB (Shibby) on the ASUS RT-AC66U

The popular TomatoUSB firmware now supports the ASUS RT-AC66U 1.75Gbps wireless router. The TomatoUSB (Shibby) firmware fully supports AC-mode (802.11ac) on 80MHz channel width.

Some features of TomatoUSB firmware:

  • Very advanced QoS (Quality of Service) configuration
  • Advanced wireless configurations (WDS, wireless client modes, etc)
  • Graphical bandwidth usage monitor
  • Printer server: access USB printer from LAN
  • Media server DLNA
  • Built-in support for USB – 3G, Storage

If you are looking for an easy to follow ASUS RT-AC66U TomatoUSB firmware flashing guide, this guide is for you.

Warning: Flashing third party firmware will void your warranty. I will not be held responsible for anything that goes wrong.


Summary of the firmware flashing steps

In the next few sections, we are going to:

  1. Download and install the ASUS RT-AC66U Firmware Restoration Utility.
  2. Download the latest TomatoUSB (Shibby) firmware for the ASUS RT-AC66U.
  3. Connect up the RT-AC66U to the computer.
  4. Flash the TomatoUSB (Shibby) firmware using the Firmware Restoration Utility.


Required equipments

You will need the following:

  • ASUS RT-AC66U Wireless Router
  • An ethernet patch cord (CAT5E cable)
  • Pen (or other pointed object) to push the reset button
  • Computer to flash the TomatoUSB firmware


Required files

You will need the following two files:

  • ASUS RT-AC66U Firmware Restoration Utility
  • TomatoUSB (Shibby) firmware

Downloading and installing the ASUS RT-AC66U Firmware Restoration Utility

  1. Using the web browser, navigate to http://support.asus.com/ServiceHome.aspx?SLanguage=en
  2. Using the search feature (“Search By”), search for “RT-AC66U” without the quotes
    You should be presented with the search results.
  3. On the search results page, click on the “Download” to navigate to the download section for RT-AC66U
  4. In the OS drop down selection box, choose the Operating System (OS) you are on (e.g. Windows 7 64-bit).
    The page should refresh and shows the list of files available for your operating system.
  5. Click on the plus (+) beside Utilities to expand the list of available downloads.
    The Utilities link should expand to show a list of files available for download.
  6. Locate the “ASUS RT-AC66U Firmware Restoration” and download it.
  7. Proceed to install the ASUS RT-AC66U Firmware Restoration Utility by launching the downloaded utility. Follow the on-screen instructions to install the ASUS RT-AC66U Firmware Restoration Utility.

Downloading the latest TomatoUSB (Shibby) firmware for RT-AC66U

  1. Using the web browser, navigate to http://tomato.groov.pl/download/K26RT-AC/
  2. Locate the latest build (e.g. 102-EN is newer than 100-EN).
  3. Navigate into the folder containing the latest build.
  4. Download the firmware (file ending with .trx). If you are not sure which to download, download the one with “AIO” in the filename.

Currently, you should have the ASUS RT-AC66U Firmware Restoration Utility installed (on your computer) and have downloaded the latest TomatoUSB (Shibby) firmware. Lets proceed to the next section.


Connecting the ASUS RT-AC66U to the computer

  1. Power off the ASUS RT-AC66U.
  2. Connect the computer (with the Firmware Restoration Utility and TomatoUSB firmware) to LAN port 1 of the ASUS RT-AC66U.
  3. Ensure the computer is configured to use DHCP.


Flashing the ASUS RT-AC66U with TomatoUSB (Shibby)

Starting the ASUS RT-AC66U in emergency firmware restore mode

  1. Power off the ASUS RT-AC66U.
  2. Press and hold on to the reset button.
  3. While holding down the reset button, power on the ASUS RT-AC66U
  4. Keep holding the reset button until the power led starts to blink / flash (on and off). When the power led starts flashing / blinking, release the reset button.

Flashing the TomatoUSB firmware using the firmware restoration utility

  1. Launch the ASUS RT-AC66U Firmware Restoration Utility on your computer.
  2. In the Firmware Restoration Utility, browse for the TomatoUSB (Shibby) firmware that you have downloaded earlier.
  3. Start the firmware flashing process.
    If a prompt appears stating that it is a incompatible firmware, acknowledge and proceed with the flash. The utility should start scanning for the RT-AC66U.
  4. Allow the firmware flashing to complete.
  5. Reboot / Power cycle the ASUS RT-AC66U wireless router when prompted.

Clearing the NVRAM

  1. After the router has completed booting up (stable led lights for wireless), power off the RT-AC66U.
  2. While holding the WPS button, turn on the RT-AC66U.
  3. Keep holding on to the WPS button for at least 30 seconds before releasing it
    The router should reboot once you release the WPS button.
  4. After the router has completed booting up, navigate to the TomatoUSB web admin ( using the default credentials (user: root, password: admin).

Enabling 5GHz band

If you notice that your 5GHz band is not showing. You will need to do the following steps.

  1. Using your web browser, navigate to the TomatoUSB web administration page of your ASUS RT-AC66U.
  2. Navigate to Administration –> Configuration.
  3. Under the “Restore Default Configuration” option, select “Erase all data in NVRAM (thorough)” and click Ok.
    The router should reboot.
  4. Once the router has finished rebooting, navigate to the TomatoUSB web administration page.
  5. Through the TomatoUSB web administration page, reboot the router using the “Reboot…” function.
    The router should reboot.
  6. Once the router has finish rebooting, the status page should reflect the 5GHz wireless band.

Congratulations. Your ASUS RT-AC66U is installed with the latest TomatoUSB (Shibby) firmware.


Treat shadowandy!

If these step-by-step guides have been very helpful to you and saved you a lot of time, please consider treating shadowandy to a cup of Starbucks.  

12 thoughts on “Upgrading ASUS RT-AC66U to TomatoUSB

  • December 5, 2013 at 7:49 am

    Thanks for this guide. It’s worth mentioning that if you’re not running Windows, the restoration utility won’t work.

    While in recovery mode, if you set a static IP you can access a firmware upgrade page at

    From there you can upload the Tomato Firmware and continue with the guide.

    You probably don’t even need the utility on Windows either.

  • February 21, 2014 at 1:24 am

    Confirming Andre’s comments.. I was able to upgrade to TomatoUSB wirelessly from my Mac using the router’s built-in firmware upgrade; no need for the Flash Restoration utility.

    Thanks guys, TomatoUSB rocks on this router.

  • February 22, 2014 at 1:34 am

    Thanks – although I restored defaults (thorough) w/o checking the 5Ghz status, and afterwards it was missing. A regular default restore had it appearing again.

  • February 22, 2014 at 1:43 am

    Also, your Donate link doesn’t work!
    “Currently PayPal accounts in Singapore are only able to send payments. This recipient is not eligible to receive funds.”
    Sorry 🙁

  • February 22, 2014 at 10:31 pm


    Thanks for informing about the PayPal link issue. Did some changes and not sure if it fixes the issue. Haha. Will wait for the next friendly guy to drop by with Starbucks. 🙂

  • February 22, 2014 at 10:32 pm


    Great to hear that! Previously, the OEM firmware does some firmware checks and denied third party firmwares. I guess they are playing friendly now. 🙂

  • May 14, 2014 at 8:32 pm

    Great article, but what are the steps to update tomato? Do I just have to upload the newest TomatoUSB-File at “Upgrade Firmware” dialogue? Should I select “After flashing, erase all data in NVRAM memory”?

  • December 8, 2014 at 3:11 pm

    Successfully installed Tomato on Asus rt-ac66r
    Only snag is that Asus stock firmware gave me bandwidht of 15MB (file transfer from my nas) while the tomato one reduced it to 10MB (note MBytes not Mbits).

  • August 12, 2015 at 4:51 pm

    Can I also apply this tutorial on my Asus RT-N18U router?

  • August 12, 2015 at 6:52 pm


    The TomatoUSB (Shibby) supports RT-N18U. The steps should be roughly the same.

Comments are closed.