Debrick Broadcom With Serial Console and CFE

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### reboot your router ### reboot your router
### point your browser to 192.168.1.1 and have at it - you're good to go! ### point your browser to 192.168.1.1 and have at it - you're good to go!
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 +[[Category:Networking hardware]]
 +[[Category:Bootloaders]]

Revision as of 19:19, 22 June 2012

Turns out there's a really elegant way to debrick your Broadcom router provided you haven't gone out of your way to damage it. Before you go running to get a JTAG cable and start messing around HairyDairyMaid or its kin, give this a try instead. It's actually kinda fun and once you've done it you'll likely no longer be afraid of bricking your routers.

Here's what it is, in summary: you're going to set yourself up so you can see the serial console on your router. Once you have that, you're going to be able to interact with a boot loader that you never knew was there, and with that bootloader, you're going to fix your router in no time flat. This method will work so long as you've not managed to destroy your router's CFE, which is possible with both JTAG and CFE itself.

How to:

  1. Set up a serial console on serial port 0 on your router
    1. Get a FT232RL breakout board or a cable that has one in it
    2. Connect RX to RX, TX to TX, and GND to GND
    3. Hook the other end up to a USB port on your computer - you now have a serial port
  2. Connect a serial terminal emulator to it
    1. Any terminal emulator will do - it's just ASCII and CR/LF - nothing fancy
    2. Set your com port parameters to 115k, 8n1
  3. Fix your bad flash with the CFE bootloader
    1. Power up your router
    2. In the boot loader window, press Control-C repeatedly 'til you see a CFE> prompt
    3. type:
      1. nvram erase
      2. flash -ctheader : flash1.trx
      3. immediately initiate a binary mode tftp put of an image to 192.168.1.1 (if it's a linksys/cisco, you may need to obtain a factory image)
      4. once it's done transferring and flashing, reboot, do the control C's to get a CFE> prompt, and execute nvram erase again
      5. reboot your router
      6. point your browser to 192.168.1.1 and have at it - you're good to go!