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Supported Versions

Hardware Highlights

ModelVersionSoCCPU MHzFlash MBRAM MBWLAN HardwareWLAN2.4WLAN5.0100M portsGbit portsModemUSB
RT-AC51UMediaTek MT7620A5801664MediaTek MT7620A, MediaTek MT7610Eb/g/na/n/ac5--1x 2.0


ASUS Firmware Restoration tool

Easiest solution for Windows users, confirmed working as of June 2019.

  1. Download the ASUS firmware restoration tool (
  2. Before using the tool you need to do the following:
  3. Unplug your computer from the router
  4. Put the router into recovery mode by: turning the power off, using a pin to press and hold the reset button, then turning the router back on while continuing to keep the reset button pressed for ~5 secs until the power light starts slowly flashing (which indicates the router has entered recovery mode)
  5. Important (if you don't do this next step the Asus firmware restoration tool will wrongly complain the router is not in recovery mode and refuse to flash it): go to Windows control panel and temporarily disable ALL other network adapters apart from the one you will use to connect your computer to the router
  6. For the single adapter you left enabled, temporarily give it a static IP and a subnet of
  7. Connect a LAN cable between your computer (make sure the ethernet port you are using on your computer is the one for the adapter you left enabled) and port 1 of the router (not the router's WAN port)
  8. Rename openwrt-18.06.2-ramips-mt7620-rt-ac51u-squashfs-sysupgrade.bin to factory.trx, open the Asus Firmware Restoration tool, locate factory.trx and click upload (if Windows 10 throws up a compatibility window asking if the tool worked, say yes)
  9. That's it (don't forget to re-enable any network adapters you disabled earlier)

TFTP method

  1. Download the OpenWrt firmware image
  2. Unplug the power cord
  3. Press the reset button, don't release it yet!
  4. Plug the power cord
  5. Wait 10 seconds
  6. Release the reset button
  7. Set a static IP (IP, Subnet, connected to first LAN port)
  8. Use tftp -client to download the firmware file
        tftp> binary
        tftp> connect
        tftp> put openwrt-18.06.2-ramips-mt7620-rt-ac51u-squashfs-sysupgrade.bin
  9. The power led flashes quickly while the router is being flashed.
  10. Flashing is successful if the power led is constantly lit.

Install LuCI

After you flashed the base image, wait until the rooter reboots and the power led is constantly lit. Connect to the router via

ssh root@

(no password) and follow the official docs for the LuCI installation here LuCI installation


LuCI Web Upgrade Process

Terminal Upgrade Process

  • Login as root via SSH on
  • Use the following commands to upgrade
    cd /tmp
    wget <sysupgrade image as shown above>
    sysupgrade lede-ramips-mt7620-rt-ac51u-squashfs-sysupgrade.bin



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toh/asus/rt-ac51u.txt · Last modified: 2019/12/13 12:27 by mamilann