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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 tested with various models (D7000, DNG3700v2, EX2700, EX6100v2, EX6120, EX6150v2, EX8000, R6020, R6080, R6100, R6220, R6400, R7000, R7000P, R6800, R8000, R8000P, R8500, RAX40, RBR40, RBS40, RBR50, RBS50, SRR60, SRS60, WAX202, WNDR3800, WNDR4300, WNDR4500v3, WNDR4700, WNR3500), but is likely to be compatible with most other Netgear devices as well.

Prebuilt binaries for Linux, macOS and Windows are available here (Npcap is required on Windows). Note that on Linux and macOS, using Homebrew is the preferred method. FreeBSD packages can be fetched and installed using the FreeBSD pkg command.

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 [10000 ms]
 -T <timeout>    Time (seconds) to wait after successfull TFTP upload [1800 s]
 -p <port>       Port to use for TFTP upload [69]
 -R <region>     Set device region (NA, WW, GR, PR, RU, BZ, IN, KO, JP)
 -S <n>          Skip <n> bytes of the firmware file
 -v              Be verbose
 -V              Print version and exit
 -L              List network interfaces
 -h              Show this screen

When using -c, the environment variables IP, PORT, NETMASK
and MAC are set to the device IP address, TFTP port, subnet
mask and MAC address, respectively.

Using nmrpflash

First, 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
Waiting for Ethernet connection (Ctrl-C to skip).

As soon as you see the Waiting for Ethernet connection. message, turn the router on. If all went well, nmrpflash will continue printing messages:

Advertising NMRP server on eth2 ... /
Received configuration request from fe:ed:1b:ad:f0:0d
Sending configuration:
Received upload request: filename 'firmware'.
Uploading EX2700-V1.0.1.8.img ... OK (3539077 b)
Waiting for remote to respond.
Received keep-alive request (11).
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).

On Debian based distros (such as Ubuntu) you can install these dependencies with

sudo apt install libpcap libnl-3
"The program can't start because wpcap.dll is missing" (Windows)

Install Npcap with "WinPcap Compatibility" enabled.

Version 0.9.13 was the last version to support Windows XP.

"nmrpflash cannot be opened because the developer cannot be verified." (macOS)

Go to  -> System Preferences -> Security & Privacy. Under the General tab, there should be a message like "nmrpflash was blocked from use because it is not from an identified developer". Click the Allow anyway button next to it, and run nmrpflash again. If that doesn't work, try this.

Please note that Homebrew is the preferred method of installing nmrpflash on macOS.

"No suitable network interfaces found."

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

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

Always run nmrpflash in the sequence described above!

If it still doesn't work, try different Ethernet ports if your device has more than one.

You can try specifying the MAC address using -m xx:xx:xx:xx:xx:xx, or, if that still doesn't work, "blind mode" using -B. Note that careful timing between running nmrpflash and turning on the router may be required in this mode.

It's also possible the bootloader itself is bricked, or that the particular device does not support the NMRP protocol.

Stuck at "Waiting for remote to respond."

The file transfer was successful, but the router still needs to actually write the data to the flash chip. Depending on the image size, this can take quite some time: times of 15 minutes and more have been reported.

Some devices will send keep-alive packets (see below) during this time, which are esentially telling nmrpflash that it's still busy flashing.

Do not reboot your device at this time, because flashing is probably still in progress (sometimes indicated by flashing LEDs). Only when nmrpflash says Reboot your device now. you can assume that the process has finished.

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

nmrpflash didn't receive a response to the initial TFTP upload request. This either indicates an IP configuration issue, or a firewall is blocking the TFTP packets from reaching the device running nmrpflash.

If you do have an active firewall, either disable it before running nmrpflash, or make sure that incoming packets for port 69 aren't being blocked.

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.

If you have a firewall installed on the computer that is running nmrpflash (such as iptables or nftables), try disabling the firewall before running nmrpflash again.

"Timeout while waiting for CLOSE_REQ."

After a successful file upload, nmrpflash waits for up to 30 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 15 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! On others, you'll only receive a few, with many minutes between each message.

"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. If it does fail, your only option is flashing an older image, which is smaller than 32 MiB.

"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 (15 minutes). 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

On Linux, developer packages for libpcap, libnl and libnl-route must be installed:

$ sudo apt install libpcap-dev libnl-3-dev libnl-route-3-dev

Then, it's as easy as

$ make && sudo make install

On Linux and macOS, you can use Homebrew to install nmrpflash:

$ brew install nmrpflash

On FreeBSD (assuming the ports infrastructure is installed and you have root permissions):

$ cd /usr/ports/sysutils/nmrpflash
$ make install

Or install the FreeBSD binary package with:

$ pkg install nmrpflash

The repository includes a CodeBlocks project file (nmrpflash.cbp). Download the latest Npcap SDK and extract it into the a folder named Npcap in the source's root directory.


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