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nmrpflash - Netgear Unbrick Utility

nmrpflash uses Netgear's NMRP protocol to flash a new firmware image to a compatible device. It has been successfully used on a Netgear EX2700, EX6120, EX6150v2, DNG3700v2, R6100, R6220, R7000, D7000, WNR3500, R6400 and R6800, R8000, R8500, WNDR3800, but is likely to be compatible with many other Netgear devices.

Prebuilt binaries for Linux, OS X macOS and Windows are available here (Npcap is required on Windows).

Usage: nmrpflash [OPTIONS...]

Options (-i, and -f or -c are mandatory):
 -a <ipaddr>     IP address to assign to target device
 -A <ipaddr>     IP address to assign to selected interface
 -B              Blind mode (don't wait for response packets)
 -c <command>    Command to run before (or instead of) TFTP upload
 -f <firmware>   Firmware file
 -F <filename>   Remote filename to use during TFTP upload
 -i <interface>  Network interface directly connected to device
 -m <mac>        MAC address of target device (xx:xx:xx:xx:xx:xx)
 -M <netmask>    Subnet mask to assign to target device
 -t <timeout>    Timeout (in milliseconds) for NMRP packets
 -T <timeout>    Time (seconds) to wait after successfull TFTP upload
 -p <port>       Port to use for TFTP upload
 -R <region>     Set device region (NA, WW, GR, PR, RU, BZ, IN, KO, JP)
 -v              Be verbose
 -V              Print version and exit
 -L              List network interfaces
 -h              Show this screen

Using nmrpflash

Download the correct firmware image for your device. When downloading from the Netgear site, the firmware is usually contained in a .zip file - extract this first. The actual firmware file will have an extension such as .chk, .bin, .trx or .img.

Now, using an Ethernet cable, connect your Netgear router to the computer that will run nmrpflash. Use the LAN port, which is often colored blue on Netgear devices. If the router has multiple LAN ports, use the one labled 1.

Next, you'll have to determine which network interface corresponds to the one connected to the Netgear router. All available interfaces can be listed using

# nmrpflash -L
eth0  c0:de:fa:ce:01:23
eth2      ca:fe:ba:be:45:67
wifi0  de:ad:be:ef:89:ab

For the rest of this example, let's assume that your router is connected to eth2, and that you want to flash a firmware image named EX2700-V1.0.1.8.img.

First of all, turn off the router. Then start nmrpflash using the following command:

# nmrpflash -i eth2 -f EX2700-V1.0.1.8.img
Advertising NMRP server on eth2 ... /

As soon as you see the Advertising NMRP server message, turn the router on. If all went well, nmrpflash will continue printing messages:

Received configuration request from fe:ed:1b:ad:f0:0d
Sending configuration:
Received upload request: filename 'firmware'.
Uploading EX2700-V1.0.1.8.img ...
Upload successful.
Waiting for remote to respond.
Remote finished. Closing connection.
Reboot your device now.

Now reboot the device, and you're good to go.

Common issues

In any case, run nmrpflash with -vvv before filing a bug report!

"Error while loading shared libraries: ..." (Linux)

You must install your Linux distribution's libpcap and libnl-3 packages (exact names will vary depending on your distribution).

"The program can't start because wpcap.dll is missing" (Windows)

Install Npcap. For nmrpflash versions prior to 0.9.14, install Npcap with "WinPcap Compatibility" enabled.

Version 0.9.13 was the last version to support Windows XP.

"No suitable network interfaces found."

Make sure the network interface is up (wireless interfaces are not supported). On Windows, try restarting the WinPcap service (commands must be run as administrator):

C:\> net stop npf
C:\> net start npf
"No response after 60 seconds. Bailing out."

The router did not respond. Always run nmrpflash in the sequence described above!

If that still doesn't work, you can try "blind mode", which can be invoked using -B. Note that you also have to specify your router's mac address using -m xx:xx:xx:xx:xx:xx. Also beware that in this mode, careful timing between running nmrpflash and turning on the router may be required!

It's also possible that your device does not support the NMRP protocol.

"Timeout while waiting for ACK(0)/OACK."

The device did not respond to nmrpflash's TFTP upload request. By default, nmrpflash will assign to the target device, while adding to the network interface specified by the -i flag. You can use -a to change the IP address assigned to the target (e.g. if your network is, specify a free IP address, such as -a, and -A to change the IP address used for the network interface.

"Timeout while waiting for CLOSE_REQ."

After a successful file upload, nmrpflash waits for up to 5 minutes for an answer from your device. You can increase this by specifying a longer timeout using -T switch (argument is in seconds).

It's entirely possible that the image was flashed successfully, but the operation took longer than 5 minutes.

"Address X/Y cannot be used on interface Z."

nmrpflash refuses to use an IP address / subnet mask combination that would make the remote device unreachable from the device running nmrpflash. For example, if the IP address of your computer is, assigning to the router makes no sense, because the TFTP upload will fail.

"IP address of X has changed. Please assign a static IP to the interface."

This can happen if the network interface in question automatically detects that the network cable has been connected, and your computer tries to reconfigure that interface (NetworkManager on Linux does this for example) - this can usually be disabled.

"Received keep-alive request."

This usually means that flashing is in progress. On some devices, you may get a few hundred keep-alive requests before it eventually finishes!

"TFTP block rollover. Upload might fail!"

By default, file transfers using TFTP are limited to 65535 * 512 bytes (almost 32 MiB). Uploading files exceeding this limit might fail, depending on the device.

"Ignoring extra upload request."

Extraneous upload requests are usually sent by the device if the image validation failed. Some possible causes are:

  • If you downloaded a firmware that's contained in an archive (a .zip for example), you must extract this file, and then use the contained firmware file as the argument to the -f parameter. Some examples for file extensions used for firmware: .chk, .bin, .trx, .img.

  • Some devices prevent you from downgrading the firmware. See if it works with the latest version available for your device. If you're already using the latest version, it might be possible to patch the version info of the firmware file. A future version of nmrpflash might incorporate an auto-patch feature for these cases.

  • Your device might expect a different image format for nmrpflash than when flashing via the web interface.

"Timeout while waiting for 0000." after "Waiting for remote to respond."

This could indicate that the device hasn't finished flashing, after the default timeout (5 minutes until version 0.9.4). Try increasing the timeout, using the -T <seconds> option, for example use -T 1800 to specify a timeout of 30 minutes.

"bind: Cannot assign requested address"

Specify the address of the router (-a), and address of your computer (-A). For example:

-A -a


-A -a

Building and installing

Linux, Mac OS X, BSDs
$ make && sudo make install

The repository includes a DevCpp project file ( Download the latest Npcap SDK and extract it into the root folder of the nmrpflash sources.


You can buy me a coffee if you want, but please consider donating the money for charity instead - Médecins Sans Frontiers comes to mind, but any other organization, local or international, that you think deserves support will do. Thank you!

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