|Version||SoC||CPU MHz||Flash MB||RAM MB||WLAN Hardware||WLAN2.4||WLAN5.0||Gbit ports||USB|
|v1||Atheros AR7161||680||8||64||Atheros AR9220, Atheros AR9223||b/g/n||a/n||5||1x 2.0|
|v2||Atheros AR7161||680||16||64||Atheros AR9220, Atheros AR9223||b/g/n||a/n||5||1x 2.0|
|v3||Broadcom BCM4718A1||480||8||64||Broadcom BCM4331, Broadcom BCM4718A1||b/g/n||a/n||5||1x 2.0|
|v4||Atheros AR9344||560||128NAND||128||Atheros AR9344, Atheros AR9582||b/g/n||a/n||5||1x 2.0|
|v5||MediaTek MT7621ST||880||16||128||MediaTek MT7603EN, MediaTek MT7612EN||b/g/n||a/n||5||1x 2.0|
The Netgear WNDR3700 has multiple different versions as shown in this table.
|v1||Atheros ar71xx platform. Also sold as WNDR37AV-100PES, WNDR3700-100PES|
|v2||Atheros ar71xx platform. Box side panel lists WNDR3700v2, also sold as WNDRMAC-100PES, WNDR3700-100PRS|
|v3||Broadcom SoC, same hardware as WNDR4000. 5 GHz wireless did not work on older builds, and probably still does not.||5 GHz issue|
|v4||Atheros platform like v1 and v2, NAND flash, same PCB as WNDR4300, but only 2T2R. May be labeled as WNDR3700-100PES on the packaging's side panel (like some v1 models).||Forum thread|
|v5||MediaTek SoC. Supported as of r49247. Radios not working reliably. This, too, may be labeled WNDR3700-100PES on the packaging.||Forum thread.|
|WNDR37AV||Netgear has sold a number of WNDR3700v2 units in boxes marked WNDR37AV. The hardware is exactly identical to version 2 (even to the point of many users finding a router physically labeled “WNDR3700” or “WNDR3700v2” inside of a box labeled “WNDR37AV”).||OEM device page, Forum thread|
|v1||Atheros AR7161 rev 2 680 MHz||64MiB||8MiB||1 WAN + 4x LAN (GBit)||AR9220 [an 2×2:2] + AR9223 [bgn 2×2:2]||Yes||Yes||Yes||here||here|
|v2||Atheros AR7161 rev 2 680 MHz||64MiB||16MiB||1 WAN + 4x LAN (GBit)||AR9220 [an 2×2:2] + AR9223 [bgn 2×2:2]||Yes||Yes||Yes||here||here|
|v3||Broadcom BCM4718A1 480 MHz||64MiB||8MiB||1 WAN + 4x LAN (GBit)||BCM4331 [an 2×2:2] + BCM4718A1 [bgn 2×2:2]||Yes||?||?||here||here|
|v4||Atheros AR9344 560MHz||128MiB||128MiB NAND||1 WAN + 4x LAN (GBit)||AR9582 [an 2×2:2] + AR9344 [bgn 2×2:2]||Yes||Yes||Yes||here||here|
|v5||MediaTek MT7621ST 880 MHz||128MiB||16MiB||1 WAN + 4x LAN (GBit)||MT7612EN [an 2×2:2] + MT7603EN [bgn 2×2:2]||Yes||Yes||?||here||here|
|Version||Flash from non-OpenWrt firmware||Upgrade from existing OpenWrt firmware|
|v1 (North America)||18.06.1 Factory image||18.06.1 Upgrade image|
|v1 (rest of the world)||18.06.1 Factory image||18.06.1 Upgrade image|
|v2||18.06.1 Factory image||18.06.1 Upgrade image|
|v3||18.06.1 Factory image||Use factory image and backup settings.|
|v4||18.06.1 Factory image||18.06.1 Upgrade image|
To create your own customized firmware, see this page.
The v2 revision may not be shown on the router bottom label. V1 and v2 seem to share the same EAN barcodes. If you have the original box, look under “Package Contents” it will say “N600 Wireless Dual Band Gigabit Router (WNDR3700v2)” for version 2, and just “WNDR3700” for version 1: WNDR3700 boxes. The Netgear firmware GUI shows the “Hardware Version” in the “Maintenance” section under “Router Status”. Also, the OEM version version for v1 is 1.0.4.x and higher, while v2 is 1.0.1.x or less.
There are rumours that a certain batch of version 1 routers have problems with the 2,4 GHz radio suddenly dying. These came in boxes marked as -01R14 or -01R15 on the barcode label. It is also said that -01R21 or -02R01 are expected to be working o.k. Board version 4 is said to be reliable. If you look at the pictures you may see at least 3 places with some kind of “version” numbering. See this spreadsheet.
Please consult →Installing OpenWrt (generic) and additionally read on here for WNDR3700 specifics.
To install simply use the stock WNDR3700 GUI to upload and install OpenWrt. Remember to use a factory.img image. Non North American users will get an warning regarding that OpenWrt identifies itself an NA, don't worry. You can just simple ignore this. Netgear WNDR3700 - OpenWrt New User(s)
Hold the 'System Restore' button on the underside of the router while powering it on, and hold the button until the power led blinks green. Then, upload the .img firmware as described in Installing OpenWrt via TFTP (see the section titled Bootloader contains TFTP server). However, note that the router will not accept the firmware when the filename is too long! Using firmware.img as filename should work. After upload, the power led is turned off and flashing starts, after that is finished the router will restart and the power led will eventually become stable green (it will be stable orange for quite some time first).
tftp 192.168.1.1 mode binary put openwrt-ar71xx-generic-wndr3700XXX-squashfs-factory.img quit
Besides generic OpenWrt firmware distribution, there are customized builds based on it and managed by individuals in the community.
Announcements and updates can be found on the OpenWrt users forum.
Typically, these builds are intended to extend functionality and/or to improve performance of the firmware, as well as provide the end-user with a preconfigured setup.
Warning: As custom builds are mostly based on the trunk (bleeding edge) branch, they are much more prone to bugs and regressions.
In order to address this, some members also release builds based on the stable branch, thus reducing the potential of regressions, yet providing the advantages of customization (check out the link to hnyman's build below).
Specifically for WNDR3700, these are the longer maintained and the more frequently updated builds (as of July 2015):
The default network configuration is:
|Interface Name||Description||Default configuration|
|br-lan||LAN & WiFi||192.168.1.1/24|
|eth0||LAN ports (1 to 4)||None|
There seems to be an issue with the internal switch. I've observed this with all kinds of laptops and OS's on a dozen access points. The problem is that sometimes traffic with a destination of a wifi client will no longer be routed to it, leading to a non-working wifi client. My advice would be to uncheck 'learning and aging' under Network → Switch in LUCI, although this effectively may turn your switch into a hub. See https://dev.openwrt.org/ticket/13612
Numbers 0-3 are Ports 4 to 1 as labeled on the unit, 5 is the internal connection to the router itself. Don't be fooled: Port 1 on the unit is number 3 when configuring VLANs. vlan0 = eth0.0, vlan1 = eth0.1 and so on.
WAN port is a gigabit port. VLANs can be configured to work on both LAN and WAN.
To create a VLANx on WAN port (eth1) declare an interface as “eth1.x”. It can be further bridged with one of the switch ports if necessary.
For the LAN interface two actions are needed:
When vlans are defined on the switch ports VLAN0 cannot be used on eth0 any more. So the default router configuration must be changed, otherwise traffic stops on the switch ports and hard reset is needed.
Here is an example. WAN port is trunked on VLAN6 and VLAN4. VLAN6 has dhcp protocol defined. VLAN4 is bridged with one of the switch ports. LAN ports 1-3 are assigned to default VLAN1 (VLAN0 is not possible for some reason). LAN port 4 is assigned to VLAN4 and bridged with WAN.
So all the traffic that goes to switch port 4 will also pass to WAN's vlan4. Switch port numbering is other way around from physical ports.
config interface lan option ifname eth0.1 option type bridge option proto static option ipaddr 192.168.1.1 option netmask 255.255.255.0 config interface wan option ifname eth1.6 option proto dhcp config interface vlan4 option type bridge option ifname "eth0.4 eth1.4" option proto static option ipaddr 192.168.20.1 option netmask 255.255.255.0 option defaultroute 0 config switch option name rtl8366s option reset 1 option enable_vlan 1 option blinkrate 2 config switch_vlan option device rtl8366s option vlan 0 option ports "5*" config switch_vlan option device rtl8366s option vlan 1 option ports "1 2 3 5t" config switch_vlan option device rtl8366s option vlan 4 option ports "0 5t"
Note: The VLAN switch configuration in Attitude Adjustment 12.09 has a bug ( https://dev.openwrt.org/ticket/7795 ), so that you need to first disable VLAN trunk and than reenable it like this:
# swconfig dev rtl8366s vlan 1 set ports '0 1 2 3t 5' # swconfig dev rtl8366s vlan 1 set ports '0 1 2 3t 5t'
Note: The switch ports are not properly shown in the Backfire 10.03.1-rc4 Luci-interface, unless you add the chip name to the 'config switch' line: like 'config switch rtl8366s'. After making that addition, Luci shows the VLANs properly at the Network/Switch page. (Reference: https://dev.openwrt.org/ticket/7830 )
The switch on wndr3700 supports following led groups:
Each group can be configured into one of 16 different modes:
A sample configuration is orange LEDs for 10/100 Mb/s connections and green for 1000 Mb/s which are blinking on activity.
swconfig dev rtl8366s port 1 set led 6 swconfig dev rtl8366s port 2 set led 9
(Notice how swconfig port number is actually the led group number and last number is the desired mode)
You can also control blinkrate of the leds with values: 0 = 43ms, 1 = 84ms, 2 = 120ms, 3 = 170ms, 4 = 340ms, 5 = 670ms.
swconfig dev rtl8366s set blinkrate 2
Note: The default LED config built into Backfire 10.03.1-rc4 (and earlier) does not match the explanation printed on the router's bottom. To make the LED behaviour match the printed explanation (green LED for 1000Mb/s), use mode 6 for port 1, mode 9 for port 2 and mode 2 for port 5. This has later been patched to trunk (bleeding edge) and Backfire branch. You can either use the swconfig command or directly edit the file '/etc/config/network'. Reference: https://dev.openwrt.org/ticket/8103
Put below in rc.local
for i in /sys/class/leds/* ; do echo 0 > "$i"/brightness; done for i in 0 1 2 3 4; do swconfig dev switch0 port $i set led 0; done
Install the package 'kmod-leds-wndr3700-usb'.
Add a USB LED configuration entry to /etc/config/system (you can edit the file manually or use Luci/System/LED_Configuration page)
config 'led' option 'name' 'USB LED' option 'sysfs' 'wndr3700:green:usb' option 'default' '0'
But that still just adds a default state to the LED. The LED will not yet turn itself on. You need to create an entry for the hotplug config:
You should add an entry to '/etc/hotplug.d/usb/10-usb' and your USB LED should be working. It won't do anything fancy (like blinking when there is disk activity), but it will turn on when a USB disk is connected and turn off when the device is removed.
Code for the file /etc/hotplug.d/usb/10-usb :
#!/bin/sh # Copyright (C) 2009 OpenWrt.org case "$ACTION" in add) # update LEDs echo "255" >/sys/devices/platform/wndr3700-led-usb/leds/wndr3700:green:usb/brightness ;; remove) # update LEDs echo "0" >/sys/devices/platform/wndr3700-led-usb/leds/wndr3700:green:usb/brightness ;; esac
The LED should now react to inserting/removing USB devices.
Note: Reference to original info: https://forum.openwrt.org/viewtopic.php?pid=105502#p105502
WNDR3700 buttons have currently (r25360) different names in Backfire and in trunk :
The button automatics is done with the
wifitoggle package. It only requires hotplugging the button event to the '/sbin/wifi' script.
To install the
wifitoggle package and configure it just follow the steps below:
opkg update opkg install wifitoggle
uci set wifitoggle.@wifitoggle.button=BTN_2 uci set wifitoggle.@wifitoggle.timer=0 uci commit wifitoggle
There is support for the WPS button removing the
wpad-mini package and installing the full version of
Here is a central openwrt wps howto: https://wiki.openwrt.org/doc/uci/wireless#wps_options
If you have a WPS enabled network device (like a modern USB dongle), you can negotiate joining the routers wireless network without manually entering SSID & passkey. You just initiate “WPS authentication” by pushing the similar WPS button on the device (or launching the process by its driver/control software). After the device has initiated the authentication process, you can accept the transaction by using the WPS button on WNDR3700. The connection should then get negotiated, and in most cases in future your PC should remember the received network settings from then on.
After finding the information and browsing the hostapd package sourcecode, the needed actions for enabling the WPS button are pretty simple:
hostapd-utils. The reason is that the tool “hostapd_cli” and some needed support functions are not included in 'wpad-mini'. WPS authentication itself is launched with a command:
hostapd_cli -p /var/run/hostapd-phy0 wps_pbc
It tells the running hostapd daemon to participate in ongoing WPS authentication sequence. It needs to be run separately for each radio (= each existing hostapd process).
root@OpenWrt:~# wifi [..] root@OpenWrt:~# hostapd_cli -p /var/run/hostapd-phy0 wps_pbc Selected interface 'wlan0' OK root@OpenWrt:~#
/etc/hotplug.d/button/50-wpswith the package. See below.
wpsin trunk. /etc/hotplug.d/button/50-wps
if [ "$ACTION" = "pressed" -a "$BUTTON" = "BTN_1" ]; then for dir in /var/run/hostapd-*; do [ -d "$dir" ] || continue logger "WPS button active: $dir" hostapd_cli -p "$dir" wps_pbc done fi
config 'wifi-iface' option 'device' 'radio0' option 'network' 'lan' option 'mode' 'ap' option 'ssid' 'public' option 'encryption' 'psk2' option 'key' 'SecretKey' option 'wps_pushbutton' '1'
If everything goes ok, you should see in Syslog not only the button events, but also succesful WPS authentication.
If you just want a straightforward simple reset button functionality, you can install the
restorefactory package and configure it:
opkg update opkg install restorefactory
Minimum configuration is to set the right value for the reset button. Reset button is 'reset' in trunk, 'BTN_0' in Backfire final.
uci set system.@restorefactory.button=reset uci commit system
After you reset to the factory defaults you have to reinstall and reconfigure the
restorefactory package. You can skip this step if you build your own image which contains a preconfigured
Using a USB-serial adapter one can easily create a USB-serial console for this device. See router_with_usb_port for more on setting it up.
To connect to the console use your favorite terminal software - mine is miniterm and the default baud rate on my system was 9600:
miniterm -b9600 -d/dev/ttyS0
|Vendor||Qualcomm Atheros||Qualcomm Atheros||Broadcom||Qualcomm Atheros|
|CPU/Speed||MIPS32 24Kc V7.4 680 MHz 1)|
|Flash-Chip||v1: Spansion S25FL064P (FL064PIF) or Macronix MX25L6405DMI-12G||Macronix MX25L12845EWI-10G||?||?|
|Flash size||8192 KiB||16384 KiB||8192 KiB||128 MiB NAND|
|RAM-Chip||2X Nanya NT5DS16M16CS-5T||?||?||?|
|RAM||64 MiB||128 MiB|
|Wireless||Atheros AR9223 802.11bgn / Atheros AR9220 802.11an||?||?||?|
|USB||Yes 1 x 2.0|
Note: This will void your warranty!
Internal J1 4-pin connector
3.3V serial port voltage !!!
COM port settings: Speed:115200, Data bits:8, Stop bits:1, Parity:none, Flow control:none
Internal J3 connector
14 Pin header
See port.jtag for more JTAG details.
Onboard Voltage Regulator is a STMicroelectronics ST1S10 which is described by ST as a
3A, 900 kHz, monolithic synchronous step-down regulator IC
Full details of the onboard ST1S10 Voltage Regulator are here
There are three total ST1S10 chips near the capacitors on the upper right of the board.
If you have a basic familiarity with RS232 signals and putting together basic electronic components, you should be able to follow these instructions to create a cable to attach to the WNDR3700's serial port.
The author of this section prefers a two-step process, that of using a USB-to-9-pin-serial (DB9) connector for the computer, and then building a separate 9-pin-serial-to-board interface. This allows you to leave the connector plugged into the board all of the time (and close the plastic case of the router!), without having a USB dongle hanging around when not using it. If you use a ribbon cable to connect to the header on the router, you can actually snake it out between the 4-port LAN jack and the WAN jack and still get the router's case back on (albeit a bit snugly), so the system looks pretty clean and polished even after adding the serial port connector.
For the computer-to-9-pin-serial part, you probably have two options:
Never ever connect RS232 directly to your router board !!! The +/- 12V RS232 will be frying your board. You need a 3V-TTL to RS232 level shifter like MAX3223 in between.
For step 1:
If you buy a premade USB-to-DB9 RS232 cable, this step is already done. (Whichever method you use, make sure that your OS has drivers for the USB converter that you are planning to use!)
If you go the CA-42 cable route, follow the “Determining the wiring assignment of your cable” steps listed in this page: http://buffalo.nas-central.org/index.php/Use_a_Nokia_Serial_Cable_on_an_ARM9_Linkstation. This page refers to a different router product, but the CA-42 cable being used is the same and your goal is to determine the pin/color assignments. You have to chop off the fancy Nokia connector and then strip wires to test wire colors with your multimeter to figure out which color corresponds to which Nokia pin number. Once you've figured that out:
Pin 6 of the Nokia connector should be wired to pin 3 on the DB9. Pin 7 of the Nokia connector should be wired to pin 2 on the DB9. Pin 8 of the Nokia connector should be wired to pin 5 on the DB9.
You should wire this cable with a male DB9 connector, which will connect to the female connector that you put on the board side of things.
For step 2:
For connecting to the WNDR3700 itself, forum user whiskas previously posted the pinout of the connector at http://img387.imageshack.us/i/26102009417.jpg/. The four pins on the board (reading from left to right in whiskas's photo) correspond to DB9 pin numbers 5, 3, 2 and no connection. You'll probably want to buy a crimp-style socket (I used a “IDC 10-pin dual row socket”, which has more pins than we need but which works fine) and a ribbon cable that connects to it. Buy a 9-pin female DB9, carefully sort out which pins in the ribbon cable need to be connected to what, and crimp them into the right place. If you use crimp-style connectors, you can do this with no tools other than steady hands, and the IDC socket will slide right onto the board without having to solder anything.
If, for whatever reason, you would prefer to avoid tftp flashing, it's possible to load a new image with ymodem (loady) or kermit (loadb). It's a good idea to use iminfo to verify the image's checksum before copying it to flash with cp.b. Remember to use the sysupgrade .bin file even if this is your initial flash from the factory firmware; the extra header in the factory .img is NOT required when flashing from U-Boot.
ar7100> loady 80800000 ## Ready for binary (ymodem) download to 0x80800000 at 115200 bps...
(Begin the ymodem or kermit transfer)
## Total Size = 0x004d0004 = 5046276 Bytes ar7100> iminfo 80800000 ## Checking Image at 80800000 ... Image Name: MIPS OpenWrt Linux-3.3.8 Created: 2012-07-01 17:49:09 UTC Image Type: MIPS Linux Unknown Image (uncompressed) Data Size: 914224 Bytes = 892.8 kB Load Address: bf070000 Entry Point: bf070000 Verifying Checksum ... OK ar7100> erase 0xbf070000 +0x004d0004 Erase Flash from 0xbf070000 to 0xbf54ffff in Bank # 1 First 0x7 last 0x54 sector size 0x10000 84 Erased 78 sectors ar7100> cp.b 0x80800000 0xbf070000 0x004d0004 Copy to Flash... write addr: bf070000 done ar7100> boot
Note that the size value (0x004d0004 in this case) will vary from one image to another. Don't omit the “+” in the erase command as it's part of the command's syntax.
According to the release notes in the NETGEAR-supplied GPL firmware, U-Boot can be upgraded using the following procedure. Note that you do not need to update U-Boot in order to install OpenWrt. Additionally, this has not yet been tested by the author of this wiki page, and you can permanently brick your router (with little hope of recovery, other than possibly finding a JTAG interface) if your U-boot image becomes corrupted:
Please burn u-boot-wndr3700-dni6-V1.7.bin Set up a tftp server on your PC, its ip address is 192.168.1.12. Entering into boot loader ag7100> set serverip 192.168.1.12 ag7100> tftp 0x80010000 u-boot-wndr3700-dni6-V1.7.bin ag7100> erase 0xbf000000 +0x70000 ag7100> cp.b 0x80010000 0xbf000000 0x50000 ag7100> reset Entering into boot loader again ag7100>bootm Then the device should be in tftp recovery mode. Please run the command "tftp -i 192.168.1.1 put WNDR3700U-V220.127.116.11.img" on MS-DOS of your PC.
NEW: More and More people reports serious issues after correctly replace ram chips on WNDR3700V2. For now users are advised to stay away from extending RAM on WNDR 3700V2 untill we will have positive feedback on this procedure.
Warning: There are reports (User batu at http://eko.one.pl/forum/viewtopic.php?id=2454) that 333Mhz chips dont work with wndr3700v2. Use 400Mhz chips if available.
I used two Samsung K4H511638D-UCCC. You can use chips from other manufacturers, but they should be DDR400 32Mx16 organization in the package TSOP-II 66pin. Chips with other organizations, such as 64Mx8, do not fit.
A list of compatible chips:
|Samsung||K4H511638D-UCCC||400Mhz - definitely not working with wndr3700v2|
|Samsung||K4H511638B-TCB3||333Mhz - not working with wndr3700v2|
|Samsung||K4H511638D-UCB3||333Mhz - definitely not working with wndr3700v2|
|Hynix||HY5DU121622CTP-J||333Mhz - definitely not working with wndr3700v2|
|Hynix||HY5DU121622CTP-D43||333/400Mhz mixed reports. Propably not working with wndr3700v2|
U-Boot report after adding memory
''U-Boot 1.1.4DNI1.6 (May 22 2009 - 16:37:44) WNDR3700U (ar7100) U-boot 0.0.12 DRAM: b8050000: 0xc0140180 **128 MB** Top of RAM usable for U-Boot at: 88000000 Reserving 315k for U-Boot at: 87fb0000 Reserving 192k for malloc() at: 87f80000 Reserving 44 Bytes for Board Info at: 87f7ffd4 Reserving 36 Bytes for Global Data at: 87f7ffb0 Reserving 128k for boot params() at: 87f5ffb0 Stack Pointer at: 87f5ff98 Now running in RAM - U-Boot at: 87fb0000 id read 0x100000ff flash size 8MB, sector count = 128 Flash: 8 MB In: serial Out: serial Err: serial Net: ag7100_enet_initialize... ''
The procedure below covers hardware revision 1. Revision 2 only has U.FL connectors for the 5 GHz antennas (PJ2 and PJ4), while the 2.4 GHz connectors are replaced with dummy connectors (presumably a Hirose testing connectors used in production). So for revision 2 the PJ5 and PJ6 connectors will have to bypassed and the coax cable soldered directly to the PCB.
You will need:
On board removes:
In place of the connector solder in U. FL connectors.
Solder shorts instead of capacitors AC77, AC113, AC148, AC186.
Solder shorts between 3 and 5-pin AS6 and AS8.
Solder shorts between 3 and 6 pin AS8 and AS10.
Drill four drill holes 6.5mm in the left side of the upper lid.
In a hole fasten cables UFL-F/RPSMA-F.
Insert the connector into the board as in the photo, and assemble the router.
Fasten to the connectors RPSMA-F antenna and turn on.
https://downloads.openwrt.org/chaos_calmer/15.05.1/ar71xx/nand/openwrt-15.05.1-ar71xx-nand-wndr3700v4-ubi-factory.img Then you probably would like to update to recent OpenWrt version. In 15.05.1 there are no known regulatory issues. If you find some, please fill up a bug.
While the WNDR3700 (and WNDR3800) are great routers, there have been a number of issues with them. Some have been recently fixed, others are still present. Note that most of these issues are related to the Atheros chipset and are not unique to the WNDR3700. Here's a short list of major issues:
Previous versions had major trouble with regards to stability in an office environment. Starting with AA 12.09 however, combined with the internal switch workaround mentioned above, these access points seem finally stable. I (Syzop) use around 20 of these on a high school which are used intensively with many associate/disassociate events.
If you happen to brick your router, do not fear. You can use TFTP file transfer to flash the router with a new firmware. Note that this TFTP recovery mode is separate from Openwrt's own “failsafe mode” and is offered by the original u-boot boot manager by Netgear, so it should be enabled with either an original Netgear firmware, a working Openwrt firmware or a bricked Openwrt firmware.
Note: WNDR3700 may also automatically enter the TFTP recovery mode, if you have flashed a bad firmware image. That is indicated by the power led blinking slowly and steadily, much slower that during a normal Openwrt boot.
For TFTP recovery you need:
Steps needed in the flashing process:
Please note that the TFTP transfer is quick, as the file is stored in RAM. However, the flashing process itself will take several minutes, after which the router should reboot automatically. Be patient – it will eventually come up as a brand new factory-fresh router with NETGEAR firmware (or Openwrt if you used the Openwrt 'factory' firmware version for debricking). Original source: https://forum.openwrt.org/viewtopic.php?pid=103295#p103295
Forum user ole.h previously posted a method for unbricking the router easily with a TFTP client. Further to his post, if you use the factory reset button method, you don't need to worry about building a serial cable, trying to tap into any crazy boot timing sequence, or do anything else particularly tricky. It is simple and the following step-by-step process (cribbed from the ole.h's earlier notes, as well as from http://cyberstorm.altervista.org/wag354g/guides/howto_unbricking_wag354g_en.txt) will get you going. This assumes that you have a copy of the stock NETGEAR firmware in the current directory.
verbose trace rexmt 1 binary connect 192.168.1.1 put WNDR3700-V18.104.22.168NA.img (or whatever the filename is that you are trying to flash)
Once done, the router will flash itself to the stock NETGEAR firmware file that you provided and reboot automatically.
Openwrt offers a generic failsafe mode, which can be launched during a few seconds early in the boot process. With WNDR3700 the correct moment is when the power LED changes from steady orange to blinking green. If you at that moment press any button (WPS, Wifi or reset) during the next two seconds, you enter the failsafe mode, in which you can access the console with telnet. Successful entrance to the failsafe mode is indicated by a rapidly blinking power LED.
WNDR3700 provides the failsafe waiting moment indication messages both to the serial console and to the network, just like described in the failsafe mode article.