DD-WRT on an ASUS RT-N66U

I originally prepared this guide after spending more time than expected sorting through conflicting instructions for an RT-N66U hardware revision B1. These are the steps that worked for that router.

Install DD-WRT

1. Connect an Ethernet cable between a LAN port on the router and the PC.
2. With the router powered off, hold the Reset button and turn it on. Continue holding Reset until the Power light begins blinking slowly, which usually takes about 15 seconds.
3. Download and launch ASUS Firmware Restoration from the official RT-N66U support page.
4. Use the utility to flash BrainSlayer V24-preSP2 build 23919.
5. Allow up to one hour for the process to finish. The Wi-Fi LEDs turn on after the router completes its boot sequence.
6. Power off the router, then power it on while holding the WPS button to clear NVRAM.
7. Wait several minutes for the router to finish rebooting.

Recovery and operating notes

• When updating from the DD-WRT web interface, rename the .trx file to .bin before uploading it at http://192.168.1.1.
• DD-WRT does not provide the hardware acceleration available in some stock ASUS builds or Asuswrt-Merlin builds. Those builds may provide better throughput on faster connections.
• The 2.4 GHz radio generally provides longer-range coverage; 5 GHz generally provides higher speed over a shorter distance.
• If QoS causes high CPU temperature or instability, disable it and retest before changing other settings.
• Router temperature is shown under Status > Router. CPU frequency controls are under Administration > Management.
• If the router appears bricked, re-enter recovery mode by holding Reset while powering it on. Use the rescue utility, or temporarily assign the PC 192.168.1.11 with subnet mask 255.255.255.0, then open the recovery interface.