If you need to do a "factory reset" on one of these you can.
Connect to the console using serial cable.
Switch on while hitting CTRL-BREAK
(on laptop hit FN-CTRL-BREAK)
Tricky, may take a few attempts - need to be hitting it really early on in the boot process.
Get rommon>
confreg 0x2142
OR
1. >confreg, >yes, >no to everything except "ignore system config info".
2. >reset
It will then reboot from an alternate configuration file, and you're in! Now however, to clear the existing setup and revert the router to a good state.
- Router>enable
- Router#conf t
- Router(config)config-register 0x2102
- Router(config)exit
- Router>write memory
- Router>reload
Useful guide:
FREE VIDEO: How to Reset or Recover your Lost Cisco Router or Switch Password
