Asus RT-AC66U B1

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The Asus RT-AC66U B1 is a hardware revision of Asus_RT-AC66U that deviates significantly from the original "A1" revision. Most notably, this revision comes with the dual-core Broadcom SoC used in the Asus_RT-AC68U.[1]


[edit] Hardware Specs[2]

  • AC1750 class rating: up to 450Mbps (2.4GHz N) + up to 1300Mbps (5GHz AC)
  • 802.11a : up to 54Mbps
  • 802.11b : up to 11Mbps
  • 802.11g : up to 54Mbps
  • 802.11n : up to 450Mbps
  • 802.11ac: up to 1300Mbps
  • Antenna x 3
  • 2.4GHz & 5GHz radios
  • 64-bit WEP, 128-bit WEP, WPA2-PSK, WPA-PSK, WPA-Enterprise, WPA2-Enterprise
  • RJ45 up to 1 Gb/s BaseT, 1xWAN, 4xLAN
  • 1 x USB3 port; 1 x USB2 port
  • Hardware Buttons: WPS, Reset, & Power
  • Flash ROM / Memory (RAM): 128 MiB / 256 MiB
  • SoC: BCM4708C0 dual-core 1 GHz ARM Cortex A9

[edit] Build Information

As the hardware of this router is similar to that of the RT-AC68U, it is recommended that you flash an RT-AC68U build. RT-AC66U builds are optimized for revision A1 and will not work with this router. Builds for RT-AC68U can be found in the typical place: Where do I download firmware?. Some of the 2017/2018 builds did not boot on this router, but 2019/2020 builds seem to be more stable. In general, the latest beta is recommended.

[edit] Known Good Builds

[edit] Firmware Installation

The latest Asus firmware prevents installation of third party firmware via the standard ASUS web UI:

To comply with regulatory amendments, we have modified our certification rule to ensure better firmware quality.
This version is not compatible with all previously released ASUS firmware and uncertified third party firmware.
Please check our official websites for the certified firmware.

To circumvent this, DD-WRT can be installed via rescue mode:

  1. Download the build you wish to install (see #Build Information above).
  2. Press the power button to turn the router off (power button out and all LEDs off).
  3. Connect your computer to a LAN port of the router.
  4. Give your computer a static IP address of, netmask (Gateway and DNS don't matter.)
  5. Press and hold the router reset button (small button next to the power button).
  6. With the reset button held, depress the router power button to turn it on.
  7. Still holding the reset button, wait for the power LED to blink. This indicates we are in rescue mode.
  8. Let go of the reset button (the power LED should remain blinking).
  9. Use a browser on your computer to navigate to You should see the CFE web UI: Image:Snap1_CFE_Webserver.png
  10. Click Restore default NVRAM values. (This is optional, but a good idea to get things back to a clean state).
  11. Upload the firmware file from 1. via the CFE web UI. The upload will take a couple of minutes, and the router will reboot automatically.
  12. Remove the static IP address for your computer to allow it to receive an address from the router.
  13. Disable and re-enable your computer's network adapter to reset the connection to the router.
  14. Use a browser on your computer to navigate to You should see the DD-WRT Web Interface.

[edit] Asus Firmware Restoration

The procedure detailed above for installing DD-WRT can often be used to install the original Asus firmware as well. In the event that that doesn't work, Asus recommends an involved procedure to restore the original firmware.

[edit] WAN-to-LAN Throughput

Current DD-WRT builds on this router cap WAN-to-LAN throughput at about 400-500Mbps. This is because cut-through forwarding solutions used by the stock firmware are not available for up-to-date Linux kernels [3]. Each packet must be processed, and the throughput is limited by the 1GHz SoC.

[edit] See Also