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Linksys WRT400N v1.0
Linksys WRT400N v1.0a
Simultaneous Dual-Band Wireless-N Router




Linksys Routers




Linksys WRT400N


Linksys WRT400N


Not Supported


Not Supported


Same as OpenWRT

NOTE: Do Not flash micro this router.
NOTE: During configuration or flashing a device, the only that should be hooked to the device is the computer and power.

Makes a great main router (gateway), will also work as a client, client bridge, repeater, repeater bridge. Although special steps are required as this is an Atheros based device.



Serial Num. = MUJ00
FCC ID = Q87-WRT400N
Industry Canada ID = 3839A-WRT400N
OEM Gemtek = WRTA-244N (WRTA-244N_V02)
CPU Type = Atheros AR7161 rev 2 (0xaa)
MIPS Rev = ?
CPU Speed = 680MHz
Bus = ?
Flash Type = Serial
Flash Chip = Winbond W25X64Vf1G 0920
Flash Size = 8MB
Max Firmware Size = 7995392 bytes
RAM Size = 32MB
RAM Chip = Winbond W94525G6EH-5
nvram Size = Set by firmware
Switch = Atheros AR8216
Port-based vlan = No
802.1q vlan = No
Ethernet Port Count = 1-10/100-WAN 4-10/100-LAN
Wired Standard = IEEE 802.3/3u
boot_wait = ?
bootloader = U-Boot
Flash Card Socket/Type = No
SD/MMC Mod Support = No
MiniPCI slots = No
PoE = No
Power = 12V/1.5A
Color of LEDs = Blue/Amber
Size = 8.07" x 1.38" x 6.30" (205 x 35 x 160 mm)
USB = No
Serial Port = 1
JTAG Port = Yes
Supported by TJTAG/Version = No
Supported by dd-wrt as of = 14039
Supported by OpenWRT as of = 10.03
Supported by Gargoyle as of = See OpenWRT
Special Features = Dual Radio, Simultaneous Transmission

Radio (ath0)

Wireless Radio = Atheros AR9223
WLAN DSP processor = ?
Antenna Connector Type = 2x2, Internal
Wireless Standard = IEEE 802.11b/g/n
WiFi Operating Frequency = 2.4GHz
 802.11n Draft = up to 300Mbps
 802.11g = 6, 9, 12, 18, 24, 36, 48, 54Mbps
 802.11b = 1, 2, 5.5, 11Mbps
Radio cor_rev = ?
Radio Capabilities = ?

Radio (ath1)

Wireless Radio = Atheros AR9220
WLAN DSP processor = ?
Antenna Connector Type = 2x2, U.FL, Internal
Wireless Standard = IEEE 802.11a/n
WiFi Operating Frequency = 5GHz
 802.11n Draft = up to 300Mbps
 802.11a = 6, 9, 12, 18, 24, 36, 48, 54Mbps
Radio cor_rev = ?
Radio Capabilities = ?

Links of Interest


Flashing DD-WRT

Files needed:

  1. Do a Hard reset or 30/30/30 on the router
  2. Set a static IP on your computer to Subnet mask should be
  3. Connect the lan cable from your computer to a LAN port of your router. Make sure your router is plugged in. Nothing should be connected to your computer or the router except the lan cable between them. Turn your firewall and any wireless computer connections OFF.
  4. Power cycle the router (uplug the power from the router for 30 seconds and then plug it back in)
  5. Open your browser to by putting that in the browser address window of your browser. You should open the linksys webgui and NOT a page that says Management Mode. If you see management mode, power cycle the router again.
  6. Leave the username blank and enter "admin" as the password
  7. Go to administration and firmware upgrade
  8. Navigate to the folder that you are using, and select linksys-to-ddwrt-firmware.bin
  9. Hit upgrade
  10. When you get a success, wait FIVE FULL minutes.
  11. If you don't get success, repeat from steps 6 up to this one. If you still don't get success, clear your browser cache. Try using a different browser as well, to navigate to
  12. When you can access the dd-wrt webgui using a browser at, power cycle the router.
  13. When you can again access the dd-wrt webgui using a browser at, do another Hard reset or 30/30/30 on the router.
  14. Go to administration and firmware upgrade
  15. Navigate to the folder that you are using, and select wrt400n-firmware.bin
  16. Hit upgrade
  17. When you get a success, wait FIVE FULL minutes.
  18. At this point you can choose to put a different build on, depending on what you needs are.
  19. Reset your computer ethernet connection to auto IP and auto DNS

Flashing OpenWRT

Flashing Gargoyle


If dd-wrt is already on the router follow these instructions. If stock firmware is on the router follow the flashing instructions.

  1. Check for recommended builds here first.
  2. Set your computer to a static IP of (or to whatever subnet the router is on) Disable all firewalls and security. Disable wireless on your computer and only have the router connected to the flashing computer by the ethernet cable between the two.
  3. Hard reset or 30/30/30 (If the router supports it, if not, reset to defults in the GUI) prior to flashing. Wait. Check for password page on re-login and change password.
  4. Flash firmware. You can use the webgui except if you have a belkin router. (For belkin use tftp.exe to flash)
  5. least three minutes. Lights should return to normal. See important2, below. Failing to wait is how most people brick their routers.
  6. Do a power cycle of the router. (Unplug the cord, count to 30 and plug it back in.)
  7. Wait for the lights to return to normal usually about 2 minutes.
  8. Hard reset or 30/30/30 again (If the router supports it, if not, reset to defults in the GUI). Wait. Check for the password page and re-login to change the password. Then you can reconfigure your settings manually.
  9. Once configured set your computer back to autoIP and autoDNS.

Important1: This Hard reset or 30/30/30 works fine for Asus router, but you do have to power cycle after the reset.

Important2: After you flash the firmware, and before you do the hard reset, the router will be building some nvram settings. YOU MUST WAIT FOR THIS TO FINISH PRIOR TO DOING ANYTHING WITH THE ROUTER INCLUDING A HARD RESET. Usually, you can tell when this process is completed by the WAN light coming on, but it does take several minutes. Go have a beer. There are starting to be more and more people who BRICK their routers by not waiting until the nvram is rebuilt, PRIOR to doing a hard reset. YOU NEED TO WAIT!

DD-WRT Reverting

TFTP Revert

TFTP flash revert reported working by LOM

GUI Revert

Special thx to LOM, who created the file.

  1. Restore factory defaults via dd-wrt GUI.
  2. Set static IP address to
  3. Goto firmware upgrade, click browse, find the revert file WRT400N_webrevert.bin, click upgrade.
  4. IMPORTANT: wait 5 minutes
  5. Enter in the web browser.
  6. At the prompt, leave the username blank and enter "admin" w/o the quotes as the password.
  7. Don't forget to set your IP back to Obtain an IP address automatically.

JTAG/Serial Info


JTAG Pinouts
nTRST   1o o2	GND
  TDI   3o o4	GND
  TDO   5o o6	GND
  TMS   7o o8	GND
  TCK   9o o10	GND
nSRST  11o o12  N/C
 DINT  13o o14  VREF
JTAG Recovery
Fixme TJTAG doesn't support this router.


Serial Pinouts
GND  4 o
 TX  3 o
 RX  2 o
VCC  1 o
Hyper terminal Setup in Windows XP
In Windows XP, Click Start Button - All Programs - Accessories - 
   Communication - HyperTerminal
Enter a name for the connection, Click ok
Choose com port you adapter is plugged into, Click ok
 Bits per second = 115200
 Data Bits = 8
 Parity = none
 Stop bits = 1
 Flow control = none
Click ok
Click File - Save As, and select a place to save it to so you 
             don't have to enter the settings again.
Putty Setup in Windows XP
After installing putty, run it
 Serial line = The COM port your using for serial (ie. COM3)
 Speed = 115200
Click on Serial under Connection
 Serial line to connect to = same as above (Serial line)
 Speed (baud) = 115200
 Data bits = 8
 Stop bits = 1
 Parity = None
 Flow control = None
Click Session
 Enter a name for your connection under saved sessions
Click Save
Click Open
Serial Recovery

To recover from a bad flash and get back to DD-WRT.....

Download openwrt-to-dd-wrt.bin, Don't worry about the name, it will get you back to DD-WRT.

Download TFTP32

Configure PC to

Install TFTP32

Set it up as server, browse to where the recovery file is.

Then in telnet(putty or hyper terminal) enter

tftpboot 0x80010000 openwrt-to-dd-wrt.bin

and if you get a successful tftp transfer then:

erase 0xbf040000 +0x600000
cp.b 0x80010000 0xbf040000 0x600000

Then enter



Linksys WRT400N v1.0b Linksys WRT400N v1.0c Linksys WRT400N v1.0d

WRT400N Serial JTAG Wrt400nv1 chip numbers Linksys WRT400N v1 dd-wrt FW mac address

Linksys WRT400N v1 stock FW wl macs Linksys WRT400N v1 stock FW wan mac Linksys WRT400N v1 stock FW lan mac

FCC Pictures

Linksys WRT400N v1.0 FCCa Linksys WRT400N v1.0 FCCb Linksys WRT400N v1.0 FCCc

Linksys WRT400N v1.0 FCCd Linksys WRT400N v1.0 FCCe Linksys WRT400N v1.0 FCCf

Linksys WRT400N v1.0 FCCg Linksys WRT400N v1.0 FCCh Linksys WRT400N v1.0 FCCi

Linksys WRT400N v1.0 FCCj Linksys WRT400N v1.0 FCCk Linksys WRT400N v1.0 FCCl

Linksys WRT400N v1.0 FCCm Linksys WRT400N v1.0 FCCn Linksys WRT400N v1.0 FCCo


Known Issues

Running dd-wrt 14144

  1. Still has constantly blinking wireless LED Ticket #1420
  2. Still has LAN MAC sudo matching ath1's MAC Ticket #1435
  3. Security LED still doesn't come on when security is set Ticket #1434
  4. Site Survey for ath0 shows double and triple the SSID's for the same MAC address Ticket #1431
  5. TX Power setting have no affect Ticket #1433
  6. 5ghz rate always says auto rather then actually speed Ticket #1436
  7. Site Survey now works for ath1 (5GHz)

Running dd-wrt 14039

Lan Speed Test Results (if setting is not listed it is default)
5GHz - ath1
Wireless Network Mode - N-Only (5GHz)
Channel Width - Turbo (40MHz)
Control Channel - upper

Laptop w/ Linksys WPC600N

Packet Length:-------104,857,600------104,857,600
Time to complete:----17.3910000-------29.7180000
Bytes Per Second:----6,029,418--------3,528,420
Bits Per Seecond:----48,235,344-------28,227,360

Problems Seen thus far on dd-wrt...

  1. MAC address on mine are screwed up like my wrt600n. wl1 and LAN MAC are the same. They weren't in the Linksys firmware.
  2. The wireless led blinks every 0.5-1 second without stop. just blinks and blinks and blinks, etc...
  3. Posting across 2.4GHz Client Bridge right now. Bridged to wrt600n.
  4. 5GHz Client Bridge very unstable, won't maintain connection with wrt600n. Keeps changing the channel when reconnecting. Maybe result of reconnection.
  5. Upgrade went smooth. Haven't tested client connections to the wrt400n.
  6. Wireless Security LED doesn't come on when security is set.
  7. 5GHz is lacking channels when set as AP

Hardware Modification

Antenna Mod

Note: This is for 5GHz band only. The 2.4GHz band antenna wires are soldered to the board.

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