Asus RT-AC66U

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Note that the two existing hardware revisions, "A1" and "B1", of this router are significantly different. This page is about revision "A1", typically referred to as RT-AC66U, without the revision. For information about the "B1" revision, see Asus_RT-AC66U_B1.


[edit] Hardware Specs

  • 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
  • Detachable 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
  • 2 x USB 2.0
  • Hardware Buttons: WPS, Reset, & Power
  • Flash ROM / Memory (RAM): 128 MiB / 256 MiB
  • SoC: BCM4706 600 MHz MIPS 74Kc architecture

[edit] Build Information

Use the asus-rt-ac66u/ folder for this router (hardware revision "A1").

  • For download locations and other info see Where do I download firmware in the FAQ
  • Research "New Build" and model/rev forum threads: do not blindly install a latest build without checking
  • Read the Peacock announcement for older recommended builds and general information.

[edit] Installation instructions

Connect an ethernet cable between the PC and router LAN port. If wireless is required, ensure strong signal.

  1. Login to the standard Asus UI page of the router (usually If this is the first time you do this it can be that you must go through a wizard to configure the standard setup.
  2. Enable Telnet by going to Advanced Settings > Administration > System > Enable Telnet and click on "Apply"
  3. Connect to the router via telnet (e.g. PuTTY) usually [1], enter username/password
    • By default both are admin. You should get the prompt (#) where you can enter the following commands.
  4. To clear the nvram: mtd-erase -d nvram
    You should get something like:
    Erasing 0x0 - 0xffff
    "nvram" successfully erased.
  5. Reboot the router: reboot
    You will lose telnet connection and the router reboots. Wait some time until this is done and then continue
  6. With your browser, login again to the standard Asus UI page of the router (usually Since we cleared nvram, you must again go through the wizard to configure the standard setup. The user/password was also reset to the default admin/admin.
  7. Navigate to: Administration > Firmware Upgrade > New Firmware File and click on Choose File and select the dd-wrt firmware file you downloaded and click on "Upload"
    Note: This step can take several minutes. Do not interrupt it. It is better to wait a minute longer than act too soon if you don't see nothing happening anymore. Once completed you should see the DD-WRT page however it can also happen that the page stays on the upload screen or even says that it can't load the next page. Wait a bit and then navigate again to
  8. This first dd-wrt page asks the new user name and password. Once these are provided you are in the dd-wrt pages.
  9. Enable Telnet by going to: Administration > Management > Remote Access > Telnet Management
  10. Open again a telnet connection to the router ( Then enter as username root and the password you used when changing the password. Note that the telnet username is always root, independent of the dd-wrt web username. You should get the prompt (#) where you can enter the following commands.
  11. Again clear NVRAM by typing: mtd -r erase nvram
    Note that after using the above command connection will be lost which is the expected behavior
  12. Reboot the router.
  13. With your browser, log back into the dd-wrt admin panel, you’ll need to reset again the username and password again.

You should now have a dd-wrt clean install.

[edit] Printing

Printer Sharing gives a general description how to configure the router to connect a printer on the USB port. However it describes too much and things that are not needed or even not working for this router. Following procedure works with firmware: DD-WRT v24-sp2 (03/29/14) giga, the latest version at the moment of writing.

So here a more specific description how to enable printing.

On the web interface of the router (

  • Enable "Core USB Support", "USB Printer Support" on the Services, USB tab (all items under "USB Support" except for "USB Storage Support").
  • It is *not* necessary to enable JFFS2 support via Administration, Management
  • Check that telnet or Secure Shell is enabled via Services, Service. SSHd and Password Login must be enabled
  • Connect your printer to the router
  • Reboot the router via Administration, Reboot Router

Via a telnet/ssh client (for example putty under Windows) connect to the router:

  • login as: root
  • password: <your password that you use to login to the web interface>
  • check if your printer was recognized:
 root@my-ddwrt-router:~# dmesg | grep usb
 usbcore: registered new interface driver usbfs
 usbcore: registered new interface driver hub
 usbcore: registered new device driver usb
 usb usb1: configuration #1 chosen from 1 choice
 usb usb2: configuration #1 chosen from 1 choice
 usb 2-1: new full speed USB device using ohci_hcd and address 2
 usb 2-1: configuration #1 chosen from 1 choice
 usblp0: USB Bidirectional printer dev 2 if 0 alt 1 proto 2 vid 0x047E pid 0x1001
 usbcore: registered new interface driver usblp

This indicates that a printer is detected on the USB port

  • Now enter
 root@my-ddwrt-router:~# netstat -an
 Active Internet connections (servers and established)
 Proto Recv-Q Send-Q Local Address           Foreign Address         State
 tcp        0      0  *               LISTEN
 tcp        0      0    *               LISTEN
 tcp        0      0    *               LISTEN
 tcp        0      0    *               LISTEN
 tcp        0    268     ESTABLISHED
 tcp        0      0     TIME_WAIT
 tcp        0      0     TIME_WAIT
 tcp        0      0     TIME_WAIT
 tcp        0      0     TIME_WAIT
 tcp        0      0     TIME_WAIT
 tcp        0      0     TIME_WAIT
 tcp        0      0     TIME_WAIT
 tcp        0      0     TIME_WAIT
 tcp        0      0     TIME_WAIT
 tcp        0      0     TIME_WAIT
 udp       0      0*
 udp       0      0    *
 udp       0      0    *
 raw       0      0   *               255
 Active UNIX domain sockets (servers and established)
 Proto RefCnt Flags       Type       State         I-Node Path
 unix  3      [ ]         STREAM     CONNECTED       1178
 unix  3      [ ]         STREAM     CONNECTED       1177
 unix  2      [ ]         DGRAM                      1161

We are especially interested in the line

 tcp        0      0  *               LISTEN

It is saying that a service via tcp is listening on port 9100

  • And at last enter
 root@my-ddwrt-router:~# ps | grep p9100d
 927 root      1108 S    p9100d -f /dev/lp0 0 -t 5

This also indicates that a process p9100d is running looking at port /dev/lp0 which is a printer port

  • You don't have to install anything via ipkg or any other script. Everything is installed by default. So if you don't have the expertise to telnet/ssh to your router, don't despair, it is only to make sure that your router recognises your printer on the USB port.

To install the printer under Windows, use the following procedure:

Windows 7

  • Open Control Panel, Devices and Printers
  • Choose Add a printer
  • Add a local printer
  • Create a new port
  • Type of port: Standard TCP/IP Port
  • Hostname or IP address:
  • Make sure that the checkbox to query the printer and select a driver is not checked
  • Wait until the detection is done. It will say that the device is not found. Don't despair
  • Choose Custom and then click Settings
  • Make sure that Protocol Raw is selected and Port 9100 is entered. That will be proposed.
  • Leave all other settings also as they were and press OK
  • Click Next.
  • Choose the printer driver for your printer.
  • Click Next
  • Give your printer a name
  • You don't have to share the printer
  • Next
  • You can set it as default printer
  • Finish

Don't forget that your routers default address is and its port is 9100

[edit] Links and Notes

NOTE: The hardware WPS button method of clearing nvram on the RT-AC66U works correctly up to version r26339. In later versions, the WPS method clears the 5GHz Wi-Fi radio to "2.4 GHz TurboQAM". This can be remedied by flashing r26339 on the unit and again clearing nvram before upgrading to a later release.

NOTE:The HTTPS access to DD-WRT's Web UI per the checkbox on the Administration page is broken in early versions. To prevent lockout, verify HTTPS access before disabling the HTTP checkbox. HTTPS is verified working in r26339 and later.

[edit] Category