When would you need this: When you are recovering a lost password and the usual ‘Ctrl-Break’ key combination is not working.
Special Requirements: None.
First of all, you have to make sure that you are pressing the correct key sequence. There are few, slightly different, keys to press to break the router boot sequence in different routers and different terminal emulation software. The table below shows the complete list of different keystrokes to interrupt the router boot sequence.
Read the rest of the article in the Router Geek Book: Guide to Cisco Routers Configuration