Cisco 1721 Router: Clearing the Config

This post details the process for removing the current configuration from a Cisco 1721 router. The end result is a 'vanilla' router configuration.

1. connect the router to a com port on the pc/laptop using the console cable
2. open Windows HyperTerminal (or other) and connect to COM1
3. enter ROMMON mode: power on the router and press the CTRL+BREAK keys within 5 seconds of the router booting up - this will display the following prompt: rommon 1>
   
4. enter: confreg 0x2142 - the following message is dispayed: "You must reset or power cycle for new config to take effect"
5. enter "i" or "reset" - the router will reboot and load the IOS but without loading the startup-config
6. eventually, the following prompt appears: "Would you like to enter the initial configuration dialog?" enter "n" for "no" and press Return when prompted. The following prompt is displayed: Router>
7. enter privilege exec mode: type "enable" at the prompt (note: no password required!)
   
   the following are the commands to enter at the prompts (the correct prompt is shown in each case):-
   
   
8. Router#write erase
9. enter (erase takes a few seconds...)
   
10. Router#conf t
11. Router(config)#config-register 0x2102 (resets the config register so that the next time the router boots, it will load the startup-config)
12. CTRL+Z
    
13. Router#write mem
14. Router#copy ru st
15. Router#reload (reboots the router)

To check the current config:-

1. Router>enable
2. Router#sh ru (shows the current running config)
3. Router#sh ver (shows the router version information)

All done!

References:
RouterGod: Cisco Psychic TAC Hotline