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, to set a basic config.
8. Enter enable mode and set the router to boot from the right place
Router>enable Router>conf t Router(config)>config-register 0x2102 Router(config)>end Router>wr mem
9. Reload the router to check it worked properly
If you want to preserve the running config, follow the instructions here.