“Factory” resetting an OpenWRT router

There are many reasons to re-flash your  home router with a different OS than the one the manufacturer has cobbled together, the Misfortune Cookie attack (US-CERT) is just one of them, Having been involved in the testing of a number of domestic xDSL routers, I have a rather low opinion on the amount of care put into the default security levels of consumer devices (but that is not what this post is about).

Image Credit: commons.wikimedia.org
Image Credit: commons.wikimedia.org

I have chosen to utilise OpenWrt on one of my internal wireless access points, and – during a reconfiguration of the network, I managed to bork the settings by not paying attention. With an out-of-the-box device, there is usually a ‘Reset’ button you can hold in while powering up the device which will clear all settings and return you to the initial un-configured state. This is not quite the case with OpenWrt, but it is still a fairly easy process to return your router to a known state, and begin the configuration process again.

  • Disconnect WAN cable
  • Unplug power to router
  • Set your computers IP address to:
    • IPv4 Address:
    • Netmask:
    • Gateway:
  • Re-power your router, pressing the ‘reset’ button when the status light begin blinking (fast)
  • Using PuTTY (or your favourite *TELNET* client), connect to and you should see the OpenWrt prompt. Type the commands below (in red) to reset the router to it’s initial, preconfigured state:
root@(none):/# mount_root
jffs2 is ready
jffs2 is ready
switching to overlay
root@(none):/# firstboot
This will erase all settings and remove any installed packages. Are you sure? [N/y]
/dev/mtdblock3 is mounted as /overlay, only erasing files
root@(none):/# reboot –f
  • Unset your static IP and have fun reconfiguring your router.