How to unbrick a Buffalo WZR-HP-G300NH and install OpenWRT

So, after a failed firmware installation, all you get is a flashing red DIAG light? All is not lost, you probably don’t need any special equipment or to open the case to unbrick the Buffalo WZR-HP-G300NH. You can probably still tftp a new firmware image when the router boots up. Instructions here are for Debian, but should be easily adaptable for other Linux distros. First, download the firmware image you want to install. If you want to install OpenWRT, it is going to be the ar71xx and make sure you get the tftp version. Here is the one I used. Now you will need to make sure you have a tftp client installed:

aptitude install tftp-hpa

Now you need to configure your network to connect to the router and create a static arp entry for it. Directly connect the router to your computer by ethernet cable, but leave the router powered off. You will need the MAC address for the router, you can get it from the SSID on the label, just insert colons like: 001D12345678 = 00:1D:12:34:56:78. You will need to do this as root.

/etc/init.d/networking stop
ifconfig eth0 192.168.11.2
ifconfig eth0 netmask 255.255.255.0
arp -s 192.168.11.1 00:1D:12:34:56:78


Replace eth0 with the ethernet interface you are using, if necessary (it is probably eth0), and use the MAC address from your router, as described. But the IP address should be as shown, not based on your usual network configuration. Now change to the directory where you downloaded the firmware image and start up your tftp client and prepare to send the image to the router (don’t power it on yet). Once you start the tftp client, you will be typing at it’s command prompt.

tftp 192.168.11.1
tftp> verbose
tftp> binary
tftp> trace
tftp> rexmt 1
tftp> timeout 60
tftp> put openwrt-15.05-ar71xx-generic-wzr-hp-g300nh-squashfs-tftp.bin


(Replace the name of the image, if you are using a different one.) As soon as you hit enter on that last command, plug in the router. The tftp client will keep retrying until the bootloader on the router is ready to receive the image, then you should see the upload begin to progress. Wait a few minutes and the router should reboot. Now you can turn your normal networking back on.

/etc/init.d/networking start

If you installed OpenWRT, the default IP for the router will now be 192.168.1.1, not 192.168.11.1. If your image included LuCI, like the one I used, you can now point your web browser to that IP to access the web interface. Now you have not only unbricked your router, but you are free to enjoy all of the awesomeness of OpenWRT!

Most of the instructions here are based on this post, many thanks to the author!