How to properly flash OpenWrt onto ASUS routers.

Tested with RT-AC750.

If you're using the RT-AC750 like me, use the RT-AC51U firmware, they're the exact same.

Disclaimer: I am not responsible for bricking your device, the information below worked for me, and will probably work for you.

I've recently flashed OpenWrt onto my RT-AC750 and had to spend a long time understanding how to actually flash it. I decided to create this repository to help myself/others in the future with the flashing process.

Prequisites:

• A computer or VM running Windows 10
• A working CAT5e/CAT6 cable
• A working ASUS router

Downloading the OpenWrt firmware

First, (assuming you didn't already) go to OpenWrt's firmware download page and find your device. In this guide I'll use the device I flashed, the RT-AC5750. After finding your device page, look for "Firmware OpenWrt Upgrade" and download the file ending on sysupgrade.bin

Downloading the ASUS Restoration Tool

Once you've downloaded the OpenWrt firmware

1. Go to ASUS's website
2. Click the magnifying glass and search your router model

On the router's page, click "Support" (next to "Review")

1. On the "Support" page, select "Driver & Utility"
2. Choose your OS (preferrably Win10 64-bit)
3. In the "Software and Utility" part, find "ASUS Firmware Restoration version" and download/unzip it
   • You may have to click "Show all"
4. Run the tool and install the program
   • The program is stored in C:\Program Files (x86)\ASUS\Wireless Router\Firmware Restoration by default

Flashing OpenWrt onto your router

After you've downloaded both things above, it's time to actually flash OpenWrt.

Optional: Clear the NVRAM (router configuration)

• Plug the power cable out, then hold the WPS button
• While holding the WPS button, plug the cable in again and power the router on
• Hold the WPS button for 30sec MAX
• Your router should be blinking fast as long as you hold WPS
• The NVRAM was cleared.

Flashing OpenWrt

You should disable any other network interfaces just in case

1. Put your router into recovery mode

   • Plug the power cable out
   • Hold the reset button with a pin
   • While holding reset, plug the cable in
     • While in recovery mode, your router should blink slowly.

2. Plug in a RJ45 cable into LAN1 slot on your router

3. Open the ASUS Restoration Tool

   • Select the OpenWrt firmware
   • Click "Upload"
   • Note: Some sites like OpenWrt wiki / YouTube say you should set a static IP.
     For me it worked without that, maybe because I'm using a Win10 VM with a TAP interface.

Congratulations, you've successfully flashed OpenWrt!