Reset a Cisco 2800 series router to factory default without the enable password

So you have a router you want to reset, but don't know the enable password. Here's what to do:

1. Connect to the serial console.

2. Power off the router and then power on.

3. Send the router a BREAK. This should bring you to the rommon prompt

4. Type this command at the rommon prompt in order to boot from Flash.

  rommon 1 > confreg 0x2142

5. Reset the router.

  rommon 2 > reset

6. The router should now boot into the Initial config dialogue:

  Would you like to enter the initial configuration dialog? [yes/no]: yes

7. Follow the prompts.

If you want to preserve the running config, follow the instructions here.