Table of Contents

Installing OpenWrt via TFTP

Go back to generic.flashing

TFTP is a very simple protocol; simple enough to be implemented in small boot loaders. The basic idea is as follows:

  1. Router is powered on
  2. Bootloader prepares startup of firmware code
  3. For a few seconds it initializes the wired lan ports
    • This doesn't happen instantly but a short time during startup/boot
    • The network settings are not always the same as OpenWRT's defaults
  4. It listens to TFTP requests for transferring a flash image
  5. Either
    1. It receives an image to flash and flashes it
    2. or continues booting the device normally if the TFTP communication timed out
      • Provided the currently loaded firmware is valid
      • If not valid behavior varies based on bootloader. Some wait for a flash via tftp while others just show an error diag light and wait for a reboot.
      • See Bootloader functionality for more details about the bootloader

This section describes actions that might damage your device or firmware. Proceed with care!

You must determine whether your hardware's bootloader has a TFTP client or server. Consult your specific model's OpenWRT Wiki page for details on necessary settings and the TFTP type offered if any.

This documentation will use example IP addresses according to RFC5737. Please consult your model's wiki documentation for actual IP addresses specific to your device.

FIXME Cleanup IP addresses as 192.168.1.x is common, but not universal. Use of RFC5737 might be more appropriate or just italic ipv4.x.y.z indicators.

Bootloader contains TFTP client


For example the bootloader implementation of the DIR-300 redboot contains a TFTP client. Two steps:

  1. first you install and start a TFTP server (or daemon) on your host and place the image(s) to be flashed in the <root directory> of this software (you may be required to do this as root). Example:
    sudo apt-get install tftpd-hpa tftp
    sudo cp ~/uboot/arch/arm/boot/uboot.img /var/lib/tftpboot
  2. Test the server:
      tftp localhost
    tftp> get uboot.img
    tftp> quit
      cmp /var/lib/tftpboot/uboot.img uboot.img
      # no output other then a prompt means it worked correctly
  3. connect to the bootloader, and tell it to get the images on your harddisk via its TFTP client (in case of the DIR-300 you obtain a connection via telnet on the non-default port 9000). Example:
    telnet 9000
    Redboot> load uboot.img
  4. after successful installation of OpenWrt, do not forget to deactivate the TFTP server again!


In case of the xxx Step 3 from Example 1 above is not applicable. There is no console to login to, the bootloader will automatically try to get a firmware over TFTP from a pre-configured IP address at every boot.


tftpd server on Mac OS X Lion

Note: places a pleasing GUI on top of the native OSX tftpd. There's a writeup of using at If you prefer to use the command-line, read on…

OS X Lion comes with a tftpd but its disabled by default. Like most services in OS X, tftpd is controlled by launchctl. The configuration with which the daemon is lauched is in /System/Library/LaunchDaemons/tftp.plist and the the identifier is

before you make changes to the config run:

sudo launchctl unload -F /System/Library/LaunchDaemons/tftp.plist


sudo launchctl load -F /System/Library/LaunchDaemons/tftp.plist

to stop tftpd run:

sudo launchctl stop

to start tftpd run:

sudo launchctl start

Here is an example config file that will work:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "">
<plist version="1.0">

Differences from the default include removing this, to enable the service:


Add this to the ProgramArguments array to make it log to /var/log/syslog.log


Place the openwrt image file you want to serve in:


Notice that even after running launchctl start you will not see tftpd running when executing ps aux | grep tftpd because of the way launchctl works. tftpd is in fact not running but launchctl will launch it as soon as it is required.

In some cases, when the output on the serial console is grabbled you can still act on faith and executer the following commands, which will work in most cases:

setenv ipaddr

setenv serverip

tftpboot 0x80000000 openwrt-xxx-generic-xxx-squashfs-factory.bin
erase 0x9f020000 +0x332004
cp.b 0x80000000 0x9f020000 0x332004
boot.m 0x9f020000


Bootloader contains TFTP server

The basic procedure of using a tftp client to upload a new firmware to your router:

  1. Unplug the power to your router
  2. Plug the Ethernet connection from your computer (acting as tftp client) into a LAN port on your model. See your model's OpenWRT wiki for details on which port to use
  3. Start your tftp client on your computer
  4. Give it the router's address (specific to model and bootloader, see your model's wiki page)
  5. Set mode to octet/binary
  6. Tell the client to resend the file until it succeeds
  7. "put" the file
  8. Plug-in your router while having the tftp client running and constantly probing for a connection
  9. The tftp client will receive an ack from the bootloader and starts sending the firmware


The TFTP commands vary across different implementations. Here are some examples:


The network link must be up and established during power up. One way to ensure this happens is to use a switch or hub inbetween your computer and the device you are flashing as this will leave the link established when you power off the device.

Another option is to disable network manager in Linux (or use a distro/LiveCD that doesn't have it). Some commands that may disable it (depends on the distribution of Linux used):

Preparation Steps
  1. Configure a static IP to match your *bootloaders* network
    • ifconfig eth0 ipv4.x.y.z netmask
    • See your device model's OpenWRT wiki page for specific settings
  2. Sometimes it helps to have a preconfigured arp entry to increase your changes of catching the tftp window
    • arp -s ipv4.x.y.1 20:aa:bb:cc:dd:00
      • Check your device model's OpenWRT wiki page for correct IP and MAC addresses
Using atftp

Advanced TFTP

Source Code care of OpenWRT

As a single command-line:

atftp --trace --option "timeout 1" --option "mode octet" --put --local-file openwrt-xxx-x.x-xxx.bin IPv4.x.y.z

Step by step:

connect IPv4.x.y.z
mode octet
timeout 1
put openwrt-xxx-x.x-xxx.bin

Using netkit's tftp

As a single command-line:

echo -e "binary\nrexmt 1\ntimeout 60\ntrace\nput openwrt-xxx-x.x-xxx.bin\n" | tftp IPv4.x.y.z

Step by step:

tftp IPv4.x.y.z
rexmt 1
timeout 60
Packet tracing on.
tftp> put openwrt-xxx-x.x-xxx.bin

Setting "rexmt 1" will cause the tftp client to constantly retry to send the file to the given address. As advised above, plug in your box after typing the commands, and as soon as the bootloader starts to listen, your client will successfully connect and send the firmware.

Some devices will also respond to ping while others do not.

Note: for some versions of the CFE bootloader, the last line may need to be "put openwrt-xxx-x.x-xxx.bin code.bin". If this does not work try other variations instead of code.bin - e.g. openwrt-g-code.bin or openwrt-gs-code.bin.

One CFE version only worked after renaming the '….bin' file to 'code.bin'. From Linux Ubuntu I then used the command 'tftp -m binary -c put code.bin' and the transfer process came to life.

Using curl

curl -T openwrt-xxx-x.x-xxx.bin tftp://IPv4.x.y.z


On Mac OS X, you should be able to flash the router with the command line tftp client, which behaves identically to netkit's tftp above.

Some people have had problems with the command line tftp client, however, and recommend using MacTFTP Client instead:

Many Macs will disable the Ethernet card when the router is powered off and will take too long to re-enable the card, causing the TFTP transfer to fail with an "Invalid Password" error. Many people have had success if they manually configure their network card (in the "Ethernet" tab of "Built-in Ethernet" in System Preferences' Network panel) to:

Alternatively, you can connect the router to the Mac via a hub or switch; see below for more information.


There are multiple tftp clients that you can choose from. See the What TFTP client should I use to flash my device? section for options.

  1. Plug in your Windows network interface into the appropriate port on the device you will be flashing
  2. Static IP your wired Ethernet interface to an appropriate IP address on the same network as your bootloaders network
    • Example: Your bootloader has an IP of (netmask of so your Windows network configuration would use
    • See your device's OpenWRT wiki page for specific settings
  3. Open an elevated command prompt
    • Start, Run, "cmd" on Windows 2000,XP,2003
    • Start, search on "cmd", ctrl+shift+enter on Vista, 7, 2008, etc.
  4. arp -s <bootloaders ip address> <bootloaders mac address> <your Windows static IP address>
    • Assists in avoiding delay in reaching tftp server on device
    • Windows MAC addresses use dashes instead of colons (ex: 00-00-00-00-00-00)
    • Windows 7 and other similar versions may require
      • netsh interface ipv4 add neighbors "Local Area Connection" <bootloaders ip address> <bootloaders mac address>
  5. Disable Windows media sensing (shouldn't be necessary if you have a switch in the middle)
    • netsh interface ipv4 set global dhcpmediasense=disabled
    • netsh interface ipv6 set global dhcpmediasense=disabled
  6. Disable Windows firewall and any other firewalls on your client machine
  7. Unplug your router
  8. Run your tftp program
  9. Plug in router immediately after tftp program begins put attempts
  10. Flash usually takes a few minutes. See your device's OpenWRT wiki page for specifics
  11. You will probably want to re-enable Windows media sensing and revert your other network changes


Don't forget about your firewall settings, if you use one. It is best to run the "put" command and then immediately apply power to the router, since the upload window is extremely short and very early in boot.

TFTP Error Reason
Code pattern is incorrect The firmware image you're uploading was intended for a different model.
Invalid Password The firmware has booted and you're connected to a password protected tftp server contained in the firmware, not the bootloader's tftp server.
Timeout Ping to verify the router is online
Try a different tftp client (some are known not to work properly)
Timeout Ping to the router works
NetworkManager (Linux) may still be running causing autosense. Try again with manual configuration.

Some machines will disable the ethernet when the router is powered off and not enable it until after the router has been powered on for a few seconds. If you're consistantly getting "Invalid Password" failures try connecting your computer and the router to a hub or switch. Doing so will keep the link up and prevent the computer from disabling its interface while the router is off.

Before you go searching for a hub to keep your link live, try setting your TCP/IP setting to a static IP (;; [gateway]) method instead of DHCP.

:!: If you can flash your router and after that it says "Boot program checksum is invalid" or "Invalid boot block on disk" on serial console try a different tftp client - atftp works well. This occurs with some netkit tftp packages and big firmwares.


FIXME would this be better to just exist in specific model's wiki pages?

FIXME should we create a page to list models with tftp support, noting which ones need the reset button trick?

On many routers, including the Asus WL-500g Premium v1 that I use, you flash an image by disconnecting power, press and hold down the reset button, and connect the power again. Wait a few seconds and the PWR LED will start to blink. Release the reset button. The device will now have a TFTP server running on

Note that many TP-Link models are reported to support the same trick, including the TL-WR740Nv4, TL-WDR4300v1, TL-WDR3600v1, TL-WR842NDv1, TL-WR841NDv8, TL-MR3020v1, TL-MR3220v2, TL-MR3420v2, TL-WR940Nv2, TL-WR941NDv5, TL-WR1042NDv1 and possibly any other TP-Link model that has a recent firmware upgrade from the manufacturer. For a summary and ongoing experiments, see:

You’ll have to use a Ethernet cable at this point. Connect it to LAN1-LAN4, not WAN. Configure your local machine on the 192.168.1.x/24 network, for example as The router will use

$ tftp
tftp> trace
Packet tracing on.
tftp> binary
tftp> put openwrt-brcm-2.4-squashfs.trx
sent WRQ <file=openwrt-brcm-2.4-squashfs.trx, mode=octet>
received ACK <block=0>
sent DATA <block=1, 512 bytes>
received ACK <block=1>
sent DATA <block=2, 512 bytes>
received ACK <block=2>
sent DATA <block=3, 512 bytes>
received ACK <block=3>
sent DATA <block=4, 512 bytes>
received ACK <block=4742>
sent DATA <block=4743, 512 bytes>
received ACK <block=4743>
sent DATA <block=4744, 512 bytes>
received ACK <block=4744>
sent DATA <block=4745, 0 bytes>
received ACK <block=4745>
Sent 2428928 bytes in 6.2 seconds
tftp> quit

Wait one minute and restart the box by disconnecting and reconnecting power. Some documentations claim that the device should restart by itself but I have never seen this happen, no matter how long I wait.

What TFTP client should I use to flash my device?

Which ever you want! Some suggestions are given below:



TFTP command line client short Instructions

  1. Open a command window (cmd.exe)
  2. "tftp -i <bootloader IP tftp server address> PUT OpenWrt-gs-code.bin"
  3. Now you may plug in the router (unplug it first if it was plugged).

Note that some bootloaders do not respond to ping.


Getting tftp to work in MacOSX "Lion"

If you get "tftp: timeout", use below

below from

sudo launchctl load -F /System/Library/LaunchDaemons/tftp.plist

sudo launchctl start

You will get errors like this

below from

tftp: server says: File not found

to fix it use

cd /var/tftpboot touch (the file in your tmp dir that you are going to send)

chmod 777 (the file in your tmp dir that you are going to send)

then do the tftp command again (ie: # tftp -p -l /tmp/mtd1


tftpd on MacOS 10.4 "Tiger"

tftpd works out-of-the-box also on the old 10.4. Maybe the tftp dir is not yet created but this is just a mkdir. Get a root shell and issue these commands:

bash-4.2$ sudo bash
bash-4.2# mkdir -p /private/tftpboot/
bash-4.2# cp /path/to/openwrt-image /private/tftpboot/
bash-4.2# launchctl load -F /System/Library/LaunchDaemons/tftp.plist 
bash-4.2# ps axu|grep ftp
root     23494   0.0  0.0    27696    152  ??  Ss    4:34PM   0:00.00 launchctl load -F /System/Library/LaunchDaemons/tftp.plist
root     23496   0.0  0.0    38604      4  p3  R+    4:34PM   0:00.00 grep ftp
bash-4.2# launchctl start
bash-4.2# ps axu|grep ftp
root     23494   0.0  0.0    27696    152  ??  Ss    4:34PM   0:00.00 launchctl load -F /System/Library/LaunchDaemons/tftp.plist
root     23498   0.0  0.0    27244    464  ??  Ss    4:34PM   0:00.01 /usr/libexec/launchproxy /usr/libexec/tftpd -i /private/tftpboot
root     23500   0.0  0.0    38604      4  p3  R+    4:34PM   0:00.00 grep ftp
bash-4.2# tftp   ### just testing
tftp> get openwrt-ar71xx-generic-hornet-ub-squashfs-sysupgrade.bin
Received 7270950 bytes in 2.7 seconds

File Permissions

Check if your TFTP Server has sufficient access rights to files or directories. U-Boots TFTP Client / tftpboot can complain with:

## Error: 'Access violation' (2), starting again!