Break sequence on a Cisco 1921 ISR

A colleague made me aware of a potentially serious problem on Cisco 1921 and other ISR G2 routers. According to Field Note 63355, these devices shipped with a buggy version of ROMMON, the software that controls the boot process of Cisco routers. Here’s how Cisco describe the problem:

Routers with ROMMON version 15.0(1r)M1 fail to respond to the break sequence command received from a device connected to the console port. This failure prevents normal password recovery of the device.

If you have a 1941 you can simply pull the CF card to enter into ROMON. But what about it you have a 1921 and need to perform password recovery? the Cisco 1921 doesn’t have a CF card, and according to Cisco has no user-replaceable flash. You’re essentially forever locked out of your device.

Thankfully, there’s a workaround. If you pop open the cover of a Cisco 1921, using a Torx 10 screwdriver, you’ll see a small daugher-board. This small daughter-board, secured with a single screw, is the flash on the 1921. Remove the single screw and carefully lift out the board.

Cisco 1921 - Flash
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How To – Recover config from a Cisco router without passwords

So, you have a Cisco router that you need to extract the configuration from but have no idea what the access details might be? So long as you have physical access to the device, and a console cable you may be in luck.

The first thing to do is connect a serial cable and use something like PuTTY or Hyperterminal to connect to your device. I’m not going to describe that process herein, if you’re unsure of how to do that it’s probably best you not proceed further.

Once you’re connected to the device, you’re probably sat at a login screen. Turn off the router and remove its CF card (or press break in the boot sequence to enter ROMmon). Boot the router and without the CF card it should enter ROMmon.

You’re probably wondering what ROMmon is? ROMmon, or “ROM Monitor”, is a bootstrap program implemented in the firmware on your router that’s responsibility is to initialize hardware boot the IOS image for your device.
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