Tue, 19 Aug 2014

Installing DD-WRT on an ASUS RT-N66U

Installing DD-WRT on an ASUS RT-N66U is an exercise in patience. The installation process requires a lot of waiting, presumably for the firmware to flash onto the unit. The unit itself does not give many indications that anything is happening during the process, leading one to conclude that the device is bricked. Here are installation instructions that take into account the wait times for firmware installations.

Disclaimer: Because I was not patient at the outset of the installation, it could be the case that no intermediary firmware was required except for the final version of DD-WRT. I was not able to test this before finishing the installation.

Note: It is possible that this procedure will work best if the router is plugged into a switch and the computer that is used to configure the router is plugged into that same switch, rather than directly into the router Ethernet port.


  1. Verify the hardware version of the unit: ASUS RT-N66U H/W Ver: .B1
  2. Download and install ASUS RT-N66U B1 Utility version
  3. Download and extract Asuswrt-Merlin RT-N66U version custom firmware.
  4. Download dd-wrt.v24-22208_NEWD_2_K2.6_mega-RT-N66_64K.trx special 64k CFE compatible firmware. Standard DD-WRT builds will not work.
  5. Directly connect a PC to port 1 on the router with an Ethernet cable. Disable any wireless cards on the PC. Configure the NIC as follows:
    IP Address:
    Subnet Mask:
  6. Power off the router. Power on the router holding the reset button until the power light starts to flash. The unit will enter "rescue mode".
  7. Setup a ping test using the command line:
    ping -t
  8. Verify that the ping reply shows a TTL=100, which indicates the router is in "rescue mode".
    Reply from bytes=32 time=1ms TTL=100
  9. Start >> Programs >> ASUS Utility >> RT-N66U Wireless Router >> Firmware Restoration
  10. Browse for RT-N66U_3.0.0.4_376.45_0.trx and click "Upload" to start the firmware installation. The browser will indicate installation progress. Once the browser indicates that the upload has finished, continue to wait until the ping test indicates the operating system on the router is up and running. This could take in excess of 30 minutes. A ping test showing TTL=64 is the indication that the flash has completed:
    Reply from bytes=32 time=1ms TTL=64
  11. Clear the NVRAM by powering off the router, holding down the WPS button and powering the unit back on, continuing to hold the WPS button for 30 seconds.
  12. Verify the installation of the custom firmware worked by connecting to with a browser.
  13. Repeat the firmware upload steps 10-12 above for dd-wrt.v24-22208_NEWD_2_K2.6_mega-RT-N66_64K.trx. The flash process might take well in excess of 30 minutes. Be patient!

Helpful links:

DD-WRT on the Asus RT-N66U with 64K CFE
Asus RT-N66U - dd-wrt.com


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