What are the different ways to brick a router?

Discussion in 'Tomato Firmware' started by premudriy, Jul 8, 2009.

  1. premudriy

    premudriy LI Guru Member

    Hello everyone!

    What are the different ways to brick a router "for sure"? I've heard a few (correct me if some of them are myth):

    1. Interrupting firmware upgrade
    2. Overclocking to unhanded frequencies
    3. Restoring other router's config file directly (improper clone)
    4. Adding overly long scripts or too many firewall rules
    5. Unplugging router right after plugging it in

    I especially concerned about ways to brick router during "normal" use, i.e. like #5 above. Correct me if #5 is just a hype, but I think I saw a post somewhere (which I can't find now) where someone said that double powercycling can kill your router.

    This might seem a bit silly, but, can we make something like a big "No-No" list and summarize all possible "don'ts" in it? Maybe even make it sticky or add as one of the entries to our FAQ section. That would certainly be helpful for newcomers.
  2. mstombs

    mstombs Network Guru Member

    A variant of 1, possibly explaining 5 is interrupting a config nvram commit flash write. Flash works in sectors, the whole sector defined by an erase boundary is first reset then the whole sector is rewritten.

    No 1 should be recoverable through tftp, all others through JTAG (clearing nvram only to reset to defaults).
  3. premudriy

    premudriy LI Guru Member

    I set up a wrt54gl for this one lady. So that means that she can: unplug router, plug it back, then unplug again and it's bricked? Wow! I better tell her then. It's kind of dangerous that router has to write to nvram during boot up.

    What about original Linksys firmware? Is it also vulnerable to #5 or is it just Tomato?
  4. SgtPepperKSU

    SgtPepperKSU Network Guru Member

    I've done that many times without any trouble. There may be a very specific instant during boot that would cause problems, but it certainly isn't as dire as "plug->unplug->BRICK!!".
  5. Toastman

    Toastman Super Moderator Staff Member Member

    There have been occasions in the past where we suffered a power-outage, the power came back on and then was immediately disconnected again, perhaps a few times. While it's never bricked my routers, it would trash them in some way so that a re-installation of tomato was necessary. Since I out all routers and AP's on UPS, it has never happened again.
  6. TVTV

    TVTV LI Guru Member

    Had this happen to me once. Found the router in the morning lit up like a Christmas tree. But the problem went away after a cold reboot.
  7. kenyloveg

    kenyloveg LI Guru Member

    try to upload wrong cfe under telnet/ssh will brick your router with no doubt, while can be fixed with JTAG tool set...
  8. Planiwa

    Planiwa Network Guru Member

    Are you speaking from personal experience?
    With WRT54GL?


    Am I a Router
    or a Brick, now? Why must I
    be so black and blue?​
  9. asammar

    asammar Network Guru Member

    Can #4 above really brick a router?! I would tend to think that scripts and/or rules can potentially lock up the router but not totally brick it.
  10. premudriy

    premudriy LI Guru Member

    Asammar, I don't know the specifics, but I'd think that something like buffer overrun can happen and scripts, when written into nvram, would overwrite code past the section where they are written, erasing parts of the firmware code itself. Of course, I could be wrong about this being exactly the case for Tomato.
  11. asammar

    asammar Network Guru Member

    Thanks for the clarification. Interesting point.
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