Asus RT-N66U

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{{Languages|Asus RT-N66U}} {{Languages|Asus RT-N66U}}
[[Image:ASUS RT-N66U.jpg | right | 360px]] [[Image:ASUS RT-N66U.jpg | right | 360px]]
- 
-=Preliminary= 
-This 'Dark Night' is a very powerful piece of equipment and the NVRAM issue has been resolved, however, it presents significant risk (bricking) that requires careful adherence to the installation process. 
- 
-Note on 26-Jan-2013: Until someone updates this page (with CFE update etc.), you may want to read here: http://charleswilkinson.co.uk/2012/12/22/dd-wrt-on-the-asus-rt-n66u-with-64k-cfe/ 
- 
-====NVRAM issue==== 
-22-February-2016. Stay away from K2.6 builds for this router. Chances are you don't have one with the original bootloader and even if you do, the K3.x-big-RT-N66U.trx build will work on the router regardless of bootloader.  
-Use the builds in the ftp://ftp.dd-wrt.com/betas/2016/02-19-2016-r29134/broadcom_K3X/ folder  
- 
-15-May-2015 The command: [https://www.dd-wrt.com/wiki/index.php/Asus_T-Mobile_Cellspot#Procedure nvram get bl_version] can be issued to determine the CFE version if you have TELNET or SSH access. The Cellspot wiki contains links to many tools and articles to change the CFE. '''Please consider posting a link to a 64K CFE for future users if you have the knowledge \ resource to do so and delete this statement. 
-''' 
- 
-25-May-2013: Since BrainSlayer posted some experimental K3.X Images, the NVRAM Issue becomes almost obsolete. Please have a look at the [http://www.dd-wrt.com/wiki/index.php?title=Asus_RT-N66U#Installation_Instructions Installation Instructions] for further instructions. 
- 
-9-Apr-2013: It seems more recently manufactured units come pre-loaded with the 64K v1.0.1.3 CFE and so are not compatible with standard DD-WRT builds. Flashing a standard DD-WRT build on these devices will result in a brick. If you don't know which CFE version your unit has when running the stock firmware,anyone wishing to flash DD-WRT on this device is advised to follow this guide: http://charleswilkinson.co.uk/2012/12/22/dd-wrt-on-the-asus-rt-n66u-with-64k-cfe/ 
- 
-1-Nov-2012: Fractal has indicated that the NVRAM is resolved and that 5Ghz is working.  
-[http://www.dd-wrt.com/phpBB2/viewtopic.php?t=86437&postdays=0&postorder=asc&highlight=otrw+light&start=1022] 
- 
-30-Oct-2012: [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=163479&start=217 RT-N66 CFE Thread] Link to discussion implementing 64K: not sure that this is ready for prime time yet, however, if you try this and feel it is ready, UPDATE THIS STATEMENT and publish the procedure, limitations, and results. 
- 
-=== DD-WRT Alternatives === 
-As of this writing (June 30, 2012) user Merlin has implemented a solution, that lives with 32k NVRAM for CFE, but extends to ~60k NVRAM in firmware. 
-* download: http://www.mediafire.com/asuswrt-merlin/  
-* source code: https://github.com/RMerl/asuswrt-merlin/ 
-* home page: http://www.lostrealm.ca/tower/node/79 
- 
-As of July 16, 2012, TomatoUSB, Shibby http://tomato.groov.pl/download/K26RT-N/build5x-097-EN/Asus%20RT-N66u%2064k/ also has implemented a 64k NVRAM solution that lives with 32K NVRAM for CFE 
=Hardware= =Hardware=
-The ASUS RT-N66U is a Dual Band N-Router (2.4GHz and 5GHz bands) with lots of RAM (256Mb) and FlashRAM (32Mb), so it is well equipped to run DD-WRT +This 'Dark Night' presents significant risk (bricking) that requires careful adherence to the installation process. The NVRAM issue has been resolved, however, knowing what builds can be used must be understood well.
- +
-The ASUS RT-N66U is in the GigaBit Routing class, meaning it can route at higher speeds than a 100Mbps WAN connection can handle. [[Asus_RT-N66U#Performance|Performance]] details below.+
- +
-If you are looking for less expensive routers, that are also well suited to run DD-WRT, you might want to check out the [[Asus RT-N16]] Single Band N-Router (2.4GHz only) but still with lots of RAM (128Mb) and FlashRAM (32Mb). Even cheaper is the [[Asus RT-N10U]] Single Band N-Router with 32Mb RAM and 8Mb FlashRAM. See also [http://promos.asus.com/US/ASUS_DD-WRT/index.htm ASUS Promo] page+
-==Hardware Specifications==+==Specifications==
* Dual Band Router - 2.4GHz and 5GHz bands * Dual Band Router - 2.4GHz and 5GHz bands
* Wireless controller [http://www.broadcom.com/press/release.php?id=s474934 Broadcom BCM4331] * Wireless controller [http://www.broadcom.com/press/release.php?id=s474934 Broadcom BCM4331]
Line 49: Line 16:
* Built-in Micro SDHC socket * Built-in Micro SDHC socket
* Power supply: DC Output, 19 V, max. 1.58 A current (=> max 30W) * Power supply: DC Output, 19 V, max. 1.58 A current (=> max 30W)
 +* Serial header: 8, n, 1, no flow control, 115200.
-==Know your hardware buttons==+====Reset button for Recovery====
-'''Reset button:'''+Pressing the Reset button at powerup will put the N66U into recovery mode.
-pressing the Reset button while power-up, will put this ASUS router in recovery mode. +*Press and hold the reset button while plugging in the power, and keep pressing the reset button for about ten seconds until the power led is blinking slowly, then release the reset button. The router is now in recovery mode: go to 192.168.1.1.
-That is: press and hold the reset button, keep pressing the reset button while plugging in the power, then keep holding the reset button pressed for about ten seconds until the power led is blinking slowly, then release the reset button. The router is now in recovery mode.+====WPS button to Clear NVRAM====
 +Pressing the Red WPS button at powerup will reset (clear NVRAM) to default settings.
 +*Press and hold the WPS button while plugging in the power, and keep pressing the WPS button for about ten seconds, then release the WPS button. All settings have now been wiped, and default settings will be used.
-'''WPS button:'''+===NVRAM issue===
-pressing the Red WPS button while power-up, will clear the NVRAM. All settings are stored in NVRAM of this ASUS router. Clearing the NVRAM is the most efficient way to reset the router to default settings.+'''<font color="red">IMPORTANT: DO NOT USE K2.6 builds</font> if using CFE v1.0.1.3 (64K nvram) or NEWER!!!'''<br>
 +At launch, the RT-N66U was limited to 32k nvram. However, CFE (bootloader) version 1.0.1.3 added 64k nvram support around April 2013, but was not compatible with DD-WRT firmware at that time. For details, see these forum links to historical nvram and 64K implemention discussions: [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=86437&postdays=0&postorder=asc&highlight=otrw+light&start=1022 Fractal comments] and [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=163479&start=217 "RT-N66 CFE Thread"]
-That is: press and hold the WPS button, keep pressing the reset button while plugging in the power, then keep holding the WPS button pressed for about ten seconds, then release the WPS button. All settings have now been wiped, and default settings will be used.+This was resolved with DD-WRT K3X builds (kernel 3.x) which extended nvram to 64k, and can be used for any CFE version. It was eventually [https://www.dd-wrt.com/forum/viewtopic.php?p=1112621#1112621 extended to 256k].<br>
 +More historical info: http://charleswilkinson.co.uk/2012/12/22/dd-wrt-on-the-asus-rt-n66u-with-64k-cfe/<br>
 +'''For newer CFE version updates''' and procedures see here: [https://www.snbforums.com/threads/cfe-bootloader-update.8259/ SNB Forums]<br>
-=Installation Instructions=+====CFE Version (or Update)====
 +[[Asus_RT-N66U#DD-WRT_Alternatives|AsusWRT-Merlin]] can be installed to enable telnet and check the CFE version, and still be flashed directly to DD.
 +*In nvram: nvram get bl_version
 +*CFE partition: strings /dev/mtd0ro | grep bl_ver
-===K3.X Builds===+====K3.X Builds====
*'''Read the New Build threads on the forums''', such as [https://www.dd-wrt.com/phpBB2/viewtopic.php?t=311722 '''this''']. *'''Read the New Build threads on the forums''', such as [https://www.dd-wrt.com/phpBB2/viewtopic.php?t=311722 '''this'''].
*Find new builds in the ''Broadcom_K3X'' build folder. *Find new builds in the ''Broadcom_K3X'' build folder.
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*#[ftp://ftp.dd-wrt.com/betas/2015/02-04-2015-r26138/broadcom_K3X/dd-wrt.v24-26138_NEWD-2_K3.x_mega_RT-N66U.trx Mega] *#[ftp://ftp.dd-wrt.com/betas/2015/02-04-2015-r26138/broadcom_K3X/dd-wrt.v24-26138_NEWD-2_K3.x_mega_RT-N66U.trx Mega]
-'''9-Sep-2014''': new K3.X builds are now also available at [ftp://ftp.dd-wrt.com/betas/ FTP dd-wrt.com/betas] and [http://www.dd-wrt.com/site/support/other-downloads?path=betas%2F WWW dd-wrt.com/betas]+====K2.6 Builds====
-:::::Select: year -> release number -> broadcom_K3X -> ......RT-N66U.trx file+'''<font color="red">IMPORTANT: DO NOT USE K2.6 builds</font> if using CFE v1.0.1.3 (64K nvram) or NEWER''', plus USB does not work in K2.6 builds. Any attempt to use a USB device will cause a kernel panic (see this [http://svn.dd-wrt.com/ticket/2580 SVN ticket]. For USB, use a K3.x build, which also works around the NVRAM issues.
-'''25-May-2013''': Since the experimental [ftp://ftp.dd-wrt.com/others/eko/BrainSlayer-V24-preSP2/2013/05-27-2013-r21676/broadcom_K3X-EXPERIMENTAL/ K3.X Broadcom Builds] are out, you do not need to care what CFE you have. DD-WRT detects it automatically and extends 32KB NVRAM Version to 64KB. Which Image you have to flash, depends on your previous Image ( Stock, Merlin, DD-WRT K2.6 ).+==== DD-WRT Alternatives ====
-* If you have Stock or Merlin firmware: flash [ftp://ftp.dd-wrt.com/betas/2015/02-04-2015-r26138/broadcom_K3X/dd-wrt.v24-26138_NEWD-2_K3.x_mega_RT-N66U.trx 26138 mega].+User Merlin implemented a solution in mid-2012 to extend the original 32k NVRAM CFE to ~60k NVRAM in firmware.
 +*Homepage: https://asuswrt.lostrealm.ca/
 +*Download: https://sourceforge.net/projects/asuswrt-merlin/files/
 +*Source code: https://github.com/RMerl/asuswrt-merlin/
 +TomatoUSB [http://tomato.groov.pl/ Shibby] also implemented a 64k NVRAM solution for 32K NVRAM CFE in 2012.
 + 
 +====Historical Build Information====
 +*'''25-May-2013''': With the new experimental [ftp://ftp.dd-wrt.com/betas/2013/05-27-2013-r21676/broadcom_K3X-EXPERIMENTAL/ K3.X Broadcom builds], the CFE version is irrelevant. DD-WRT detects it automatically to extend 32KB NVRAM to 64KB. ''Which Image you have to flash, depends on your previous Image (Stock, Merlin, DD-WRT K2.6).''
* For DD-WRT K2.6: It depends how much NVRAM ( 32KB / 64KB ) you currently have.<br>For 32KB, flash [ftp://ftp.dd-wrt.com/betas/2015/02-04-2015-r26138/broadcom_K3X/dd-wrt.v24-26138_NEWD-2_K3.x_mega_RT-N66U.trx 26138 mega]. * For DD-WRT K2.6: It depends how much NVRAM ( 32KB / 64KB ) you currently have.<br>For 32KB, flash [ftp://ftp.dd-wrt.com/betas/2015/02-04-2015-r26138/broadcom_K3X/dd-wrt.v24-26138_NEWD-2_K3.x_mega_RT-N66U.trx 26138 mega].
-* If you are already on a custom 64K Build like Fractal or Kong with CFE 1.0.1.3, you need to flash [ftp://ftp.dd-wrt.com/betas/2015/02-04-2015-r26138/broadcom_K3X/dd-wrt.v24-26138_NEWD-2_K3.x_mega-nv64k.bin 26138 mega nv64k]. Since K2.6 Builds have an embedded check, you need to use those special nvXXk trailed images. On K3.X this check has been removed and you can simply upgrade from a previous K3.X to newer svn using dd-wrt.v24-YYYYY_NEWD-2_K3.x_mega.bin.+* If you are already on a custom 64K Build like Fractal or Kong with CFE 1.0.1.3, you need to flash [ftp://ftp.dd-wrt.com/betas/2015/02-04-2015-r26138/broadcom_K3X/dd-wrt.v24-26138_NEWD-2_K3.x_mega-nv64k.bin 26138 mega nv64k]. Since K2.6 Builds have an embedded check, you need to use those special nvXXk trailed images. On K3.X this check has been removed and you can simply upgrade from a previous K3.X.
 +*'''8-Mar-2015: [http://www.desipro.de/ddwrt-ren/K26/r22000++/kingkong-nv64k-RT-N66U-broadcom.trx Kong 22000++] is a good (recommended) build for the RT-N66U with 64K CFE'''<br>with fix for the serious [http://www.dd-wrt.com/site/content/heartbleed-dd-wrtdd-wrt-online-services Heartbleed vulnerability].
 +*'''9-Apr-2013:''' It seems more recently manufactured units come pre-loaded with the 64K v1.0.1.3 CFE and so are not compatible with standard DD-WRT builds. Flashing a K2.6 DD-WRT build on these devices will result in a brick.
 +*'''26-Jan-2013:''' Current versions of DD-WRT can quickly run out of 32k nvram.
 +*Build 18946 fixes the WAN port issue.
-===K2.6 Builds===+=Installation Instructions=
-USB does not work in K2.6 builds, any attempt to use a USB device will cause a kernel panic see this [http://svn.dd-wrt.com/ticket/2580 trac ticket]. If you want USB functionality with DD-WRT you'll need to use a K3.x build as the problem is fixed in K3.x builds, but won't however be fixed for K2.6 builds.+For recommended builds, read the [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=51486 Peacock Announcement], New Build, and model-specific threads.
- +
-'''8-Mar-2015: [http://www.desipro.de/ddwrt-ren/K26/r22000++/kingkong-nv64k-RT-N66U-broadcom.trx Kong 22000++] is a good (recommended) build for the RT-N66U with 64K CFE'''<br>with fix for the serious [http://www.dd-wrt.com/site/content/heartbleed-dd-wrtdd-wrt-online-services Heartbleed vulnerability].+
- +
-'''9-Apr-2013:''' It seems more recently manufactured units come pre-loaded with the 64K v1.0.1.3 CFE and so are not compatible with standard DD-WRT builds. Flashing a K2.6 DD-WRT build on these devices will result in a brick. As it is impossible to know which CFE version you unit has when running the stock firmware, anyone wishing to flash DD-WRT on this device is advised to follow this guide: http://charleswilkinson.co.uk/2012/12/22/dd-wrt-on-the-asus-rt-n66u-with-64k-cfe/ These instructions should be updated when an official build becomes available.+
- +
-'''26-Jan-2013:''' Current versions of dd-wrt from the dd-wrt website will quickly run out of nvram (because of 32Kb nvram issue). For a solution where you update CFE to 64Kb NVRAM - AND - use a version of DD-WRT that has N66_64K fix included see: http://charleswilkinson.co.uk/2012/12/22/dd-wrt-on-the-asus-rt-n66u-with-64k-cfe/ AND http://forums.smallnetbuilder.com/showthread.php?t=8259 - (someone please update the general instructions below, when the official dd-wrt is ready for general deployment on the N66U).+
- +
-Otherwise please note: The RT-N66U does REQUIRE the '''K26''' Firmware builds as Broadcom has not released drivers for the non-K26 builds. (Read more here: [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=52043 Recommended Firmwares]).+
- +
-Note: use build 18946, it fixes the WAN port issue.+
===Principle steps=== ===Principle steps===
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* Reset to Factory Default Settings or clear NVRAM * Reset to Factory Default Settings or clear NVRAM
-= Install an internal MicroSD card=+=Install an internal MicroSD card=
-'''11 Apr 2014 - Important note:'''+Important note:''' USB (and thus MMC) is not supported on K2.6 builds - it causes a kernel panic. However it is working on K3.x builds. See [http://svn.dd-wrt.com/ticket/2580 SVN ticket]
-USB (and therefore MMC) support does not work on K2.6 builds - it causes a kernel panic. However it is working on K3.x builds. See [http://svn.dd-wrt.com/ticket/2580 SVN Ticket 2580] for more info.+ 
#Open the case #Open the case
#* Unscrew the four screws at the bottom #* Unscrew the four screws at the bottom
Line 158: Line 135:
In addition to the NAS features of DD-WRT, you can use the extra space to install Optware or [[Adding_Software_Packages_using_Entware-3X|Entware-3X (recommended over Optware)]]. In addition to the NAS features of DD-WRT, you can use the extra space to install Optware or [[Adding_Software_Packages_using_Entware-3X|Entware-3X (recommended over Optware)]].
-'''11 Apr 2014:''' Please note that since USB & MMC support is not working on K2.6 builds, you cannot install Optware on K2.6 builds. USB & MCC are working on K3.x builds, however Optware support for K3.x builds is currently considered beta. Having said that, forum member kabadisha has successfully tested installation of Optware on K.3x build 23598 mega on this device using the following instructions: [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=156013 OTRW Take 2]+Without MMC on K2.6 builds, Optware can't be installed. Use K3.x builds: [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=156013 OTRW Take 2]
=Performance= =Performance=
-This router is in the GigaBit Routing class, meaning it can route at quite a bit higher speeds than a 100mpbs internet connection can handle. 
- 
<pre> <pre>
Test Description RT-N66U Test Description RT-N66U
Line 170: Line 145:
Maximum Simultaneous Connections 34,925 Maximum Simultaneous Connections 34,925
Firmware Version 3.1.0.3.90 (stock firmware number) Firmware Version 3.1.0.3.90 (stock firmware number)
-</pre> Sources: [http://www.smallnetbuilder.com/wireless/wireless-reviews/31687-asus-rt-n66u-dark-knight-dual-band-wireless-n900-gigabit-router-reviewed?start=2] Testing methods: [http://www.smallnetbuilder.com/lanwan/lanwan-howto/31103-how-we-test-hardware-routers-revision-3]+</pre>
 +[http://www.smallnetbuilder.com/wireless/wireless-reviews/31687-asus-rt-n66u-dark-knight-dual-band-wireless-n900-gigabit-router-reviewed?start=2 Sources] and [http://www.smallnetbuilder.com/lanwan/lanwan-howto/31103-how-we-test-hardware-routers-revision-3 testing methods]
-=====Overclocking=====+===Overclocking===
-Overclocking is availible, but does not work yet. CFE Bootloader is using old hndmips.c source and it does not support frequencies higher 600 MHZ. Underclocking is working so far.+Overclocking works since CFE 1.0.1.3, while underclocking worked prior to that. Overclocking may cause instability, or services (like QoS) to behave unpredictably
- +*Recommended to improve cooling or ventilation when overclocking
-'''12-Dec-2015''' Overclocking may cause QoS or other services to behave unpredictably. (QoS degradation observed at 632Mhz overclocking with K3.0-r27360 (06/18/15) big, YMMV)+*One report of QoS degradation at 632Mhz with K3.X big r27360 (06/18/15)
=Links and Notes = =Links and Notes =
Primary forum threads Primary forum threads
-* [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=86437&start=1155 Forum: RT-N66U General Discussion] 
-* [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=163479&start=451 Forum: RT-N66 CFE Thread] – Information specifically about upgrading to the 64k CFE. 
* [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=171783 One User's Guide] - A users guide for flashing Rt-N66u * [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=171783 One User's Guide] - A users guide for flashing Rt-N66u
 +* Possible ways to update CFE (once a 32k+ CFE is released for this router), see [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=86437&postdays=0&postorder=asc&start=496 LOM post]
 +*[[Linking_Routers| Linking Routers]] to cover a bigger area with WiFi
 +*Wireless tweaking: [[Basic_Wireless_Settings|Basic Wireless Settings]] and [[Advanced_wireless_settings|Advanced Wireless Settings]]
 +*External antennas: [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=43810 The CATFISH thread]
Additional forum threads Additional forum threads
Line 192: Line 170:
* [http://service.asus.com/demoui/RT-N66U/EN/index.html Asus Stock UI demo] * [http://service.asus.com/demoui/RT-N66U/EN/index.html Asus Stock UI demo]
-* WAN issue fixed in svn18835, see [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=86437&postdays=0&postorder=asc&start=214 Forum post, Eko]+==More Links==
-* Serial inside is: 8, n, 1, no flow control, 115200. +*[https://www.dd-wrt.com/wiki/index.php/Index:FAQ Frequently Asked Questions]
-* Possible ways to update CFE (once a 32k+ CFE is released for this router), see [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=86437&postdays=0&postorder=asc&start=496 Forum, LOM]+*[http://www.dd-wrt.com/phpBB2/viewtopic.php?t=51486 Peacock Announcement]: '''Required reading''' for DD-WRT on Broadcom routers!
-* Positive report of running svn18740, see [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=86437&postdays=0&postorder=asc&start=706 Forum post]+
- +
-==Generally good to know ==+
-* [https://www.dd-wrt.com/wiki/index.php/Index:FAQ Frequently Asked Questions]+
-* [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=51486 Peacock Thread-FAQ: EVERYTHING you NEED to know! Really!!] All the basics about DD-WRT on Broadcom based routers - A MUST READ Thread!!!+
-* Get the most speed out of your [[Basic_Wireless_Settings|Basic Wireless Settings]] and [[Advanced_wireless_settings|Advanced Wireless Settings]]+
-* [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=43810 The CATFISH thread - external antenna choice and use] If you need a better WiFi connection - get a more focused antenna!!!+
-* [[Linking_Routers| Linking Routers]] to cover a bigger area with WiFi +
- +
[[Category:Asus guides]] [[Category:Asus guides]]

Revision as of 00:01, 23 January 2018

Contents

Hardware

This 'Dark Night' presents significant risk (bricking) that requires careful adherence to the installation process. The NVRAM issue has been resolved, however, knowing what builds can be used must be understood well.

Specifications

  • Dual Band Router - 2.4GHz and 5GHz bands
  • Wireless controller Broadcom BCM4331
  • MIMO 3x3 on both frequencies (see Forum, BrainSlayer)
  • Gigabit LAN and WAN switching
  • 2x USB 2.0 connectors
  • CPU Broadcom 4706 @ 600MHz
  • 256MB RAM
  • 32MB FlashRAM
  • Built-in Micro SDHC socket
  • Power supply: DC Output, 19 V, max. 1.58 A current (=> max 30W)
  • Serial header: 8, n, 1, no flow control, 115200.

Reset button for Recovery

Pressing the Reset button at powerup will put the N66U into recovery mode.

  • Press and hold the reset button while plugging in the power, and keep pressing the reset button for about ten seconds until the power led is blinking slowly, then release the reset button. The router is now in recovery mode: go to 192.168.1.1.

WPS button to Clear NVRAM

Pressing the Red WPS button at powerup will reset (clear NVRAM) to default settings.

  • Press and hold the WPS button while plugging in the power, and keep pressing the WPS button for about ten seconds, then release the WPS button. All settings have now been wiped, and default settings will be used.

NVRAM issue

IMPORTANT: DO NOT USE K2.6 builds if using CFE v1.0.1.3 (64K nvram) or NEWER!!!
At launch, the RT-N66U was limited to 32k nvram. However, CFE (bootloader) version 1.0.1.3 added 64k nvram support around April 2013, but was not compatible with DD-WRT firmware at that time. For details, see these forum links to historical nvram and 64K implemention discussions: Fractal comments and "RT-N66 CFE Thread"

This was resolved with DD-WRT K3X builds (kernel 3.x) which extended nvram to 64k, and can be used for any CFE version. It was eventually extended to 256k.
More historical info: http://charleswilkinson.co.uk/2012/12/22/dd-wrt-on-the-asus-rt-n66u-with-64k-cfe/
For newer CFE version updates and procedures see here: SNB Forums

CFE Version (or Update)

AsusWRT-Merlin can be installed to enable telnet and check the CFE version, and still be flashed directly to DD.

  • In nvram: nvram get bl_version
  • CFE partition: strings /dev/mtd0ro | grep bl_ver

K3.X Builds

  • Read the New Build threads on the forums, such as this.
  • Find new builds in the Broadcom_K3X build folder.
  • 8-Mar-2015: 26138 is a good (recommended) build for the RT-N66U:
    1. Big
    2. Mega

K2.6 Builds

IMPORTANT: DO NOT USE K2.6 builds if using CFE v1.0.1.3 (64K nvram) or NEWER, plus USB does not work in K2.6 builds. Any attempt to use a USB device will cause a kernel panic (see this SVN ticket. For USB, use a K3.x build, which also works around the NVRAM issues.

DD-WRT Alternatives

User Merlin implemented a solution in mid-2012 to extend the original 32k NVRAM CFE to ~60k NVRAM in firmware.

TomatoUSB Shibby also implemented a 64k NVRAM solution for 32K NVRAM CFE in 2012.

Historical Build Information

  • 25-May-2013: With the new experimental K3.X Broadcom builds, the CFE version is irrelevant. DD-WRT detects it automatically to extend 32KB NVRAM to 64KB. Which Image you have to flash, depends on your previous Image (Stock, Merlin, DD-WRT K2.6).
  • For DD-WRT K2.6: It depends how much NVRAM ( 32KB / 64KB ) you currently have.
    For 32KB, flash 26138 mega.
  • If you are already on a custom 64K Build like Fractal or Kong with CFE 1.0.1.3, you need to flash 26138 mega nv64k. Since K2.6 Builds have an embedded check, you need to use those special nvXXk trailed images. On K3.X this check has been removed and you can simply upgrade from a previous K3.X.
  • 8-Mar-2015: Kong 22000++ is a good (recommended) build for the RT-N66U with 64K CFE
    with fix for the serious Heartbleed vulnerability.
  • 9-Apr-2013: It seems more recently manufactured units come pre-loaded with the 64K v1.0.1.3 CFE and so are not compatible with standard DD-WRT builds. Flashing a K2.6 DD-WRT build on these devices will result in a brick.
  • 26-Jan-2013: Current versions of DD-WRT can quickly run out of 32k nvram.
  • Build 18946 fixes the WAN port issue.

Installation Instructions

For recommended builds, read the Peacock Announcement, New Build, and model-specific threads.

Principle steps

For builds and more information, see here: Where do I download firmware?.
IMPORTANT: DO NOT USE K2.6 builds if using CFE v1.0.1.3 (64K nvram) or NEWER

  • Older CFE (32K nvram) can use K2.6: see the above K2.6 and K3.X sections for details
  1. Reset or select Factory Default settings.
  2. Install the trailed ASUS RT-N66U version of DD-WRT (file name ends in .trx) using either the Web GUI method or the Recover Utility method. Both methods are described below
  3. Reset again
  4. "Upgrade" to your final version of DD-WRT (filename ends in .bin) using Web GUI or Recovery Utility
  5. Reset again

IMPORTANT: Reset to clear NVRAM (or Admin->Factory Default settings) BEFORE and AFTER firmware upload.

Upload Firmware via Web GUI

  1. Reset or select Factory Default settings.
  2. Upload the .trx file using the stock web GUI. See Where do I download firmware? for links. See the build threads on the forums for recommendations.
  3. When complete, wait until the router reboots itself, which can take at least 10 minutes. You want both ping response and web gui response to know that the router is fully rebooted.
  4. Hard reset or select Factory Default settings. Wait for the router to reboot itself!!! May take 10 minutes or more

Upload Firmware via Recovery Utility

  1. Set your computer to a static IP (e.g. 192.168.1.12), subnet 255.255.255.0, default gateway 192.168.1.1
  2. Put router into recovery mode by holding down the reset button while powering up the router, wait until the power led is blinking slowly, then release the reset button.
  3. In the Asus Recover utility Access the router’s built in recovery mode by issuing 192.168.1.1 in browser field.
  4. Flash the initial DD-WRT trailed build (with N66U in the name) and upload.
  5. When complete, wait until the router reboots itself, which can take at least 10 minutes.
  6. Enter recovery mode again and flash the final DD-WRT build (big or mega with N66U in the name).
  7. When complete, wait until the router reboots itself again.
  8. Enter recovery mode again and select to Restore defaults NVRAM values
  9. Wait until the router reboots itself, which can take at least 10 minutes.
  10. Now you should be able to access the DD-WRT GUI at 192.168.1.1 to set a password.

Switching from Tomato

  1. Download the latest K3.x mega build. See Where do I download firmware? for links. See the build threads on the forums for recommendations.
  2. Navigate to the Tomato firmware update page
    • Administration > Upgrade
  3. Upload the firmware you downloaded in step 1
  4. The router will reset several times and change its IP address to the default one (192.168.1.1).
  5. Navigate to http://192.168.1.1/Factory_Defaults.asp
    • The login credentials have been reset to the default dd-wrt username/password (root/admin)
  6. Set "Restore Factory Defaults" to yes and click "Apply Settings".
Note: Many settings will carry over from Tomato to DD-WRT, but it's highly advisable to reset to factory defaults after flashing, or you risk undesired behavior and instability.

Upgrade to newer DD-WRT

  • Clear settings (Clear NVRAM)
  • Use the DD-WRT web GUI : Administration -> Firmware upgrade
  • Clear settings (Clear NVRAM)
  • svn24461 BRICKS RT-N66U. Recover possible through mini CFE webinterface.

Revert to original ASUS firmware

  • Download firmware from ASUS web site
  • Reset to Factory Default Settings or clear NVRAM
  • Use the DD-WRT web gui: Administration -> Firmware upgrade
  • Reset to Factory Default Settings or clear NVRAM

Install an internal MicroSD card

Important note: USB (and thus MMC) is not supported on K2.6 builds - it causes a kernel panic. However it is working on K3.x builds. See SVN ticket

  1. Open the case
    • Unscrew the four screws at the bottom
    • Then you want to release the plastic clips that holds the top and bottom parts together.
    • Pry the bottom case outward, which has the male clips.
    • For future access, it is recommended to either snip off the female "U" clips on the top cover, or round off the square edges on the male part of the clip with a nail file.
  2. Install MicroSD card
  3. Make use of the MicroSD card

In addition to the NAS features of DD-WRT, you can use the extra space to install Optware or Entware-3X (recommended over Optware).

Without MMC on K2.6 builds, Optware can't be installed. Use K3.x builds: OTRW Take 2

Performance

Test Description                                RT-N66U
WAN - LAN	                                       732 Mbps
LAN - WAN                                         729 Mbps
Total Simultaneous                            810 Mbps
Maximum Simultaneous Connections   34,925
Firmware Version                                3.1.0.3.90  (stock firmware number)

Sources and testing methods

Overclocking

Overclocking works since CFE 1.0.1.3, while underclocking worked prior to that. Overclocking may cause instability, or services (like QoS) to behave unpredictably

  • Recommended to improve cooling or ventilation when overclocking
  • One report of QoS degradation at 632Mhz with K3.X big r27360 (06/18/15)

Links and Notes

Primary forum threads

Additional forum threads

More Links