To resolve this issue, perform these steps:
- To erase the configuration file, issue the erase nvram: command.Reload the router by issuing the reload command.
- If this does not solve the problem, attempt to break into ROM Monitor (ROMmon) by issuing the break sequence (usually Ctrl and break from the Hyperterminal) from a console connection.Refer to the Standard Break Key Combinations section of Standard Break Key Sequence Combinations During Password Recovery.
You should see this ROMmon prompt:
- Change the configure register value to ignore the startup configuration by issuing the confreg command, as shown in this example:rommon 2> confreg 0x2142
- To reload the router, issue the reset command, as shown in this example:rommon 3> reset
- After the router boots, issue the enable command at the Router > prompt. The prompt changes to Router#, indicating that the router is now in privileged mode.
- To enter config mode, issue the config terminal command. You should now see a
- To change the configure register to recognize the startup configuration, issue the config-register command, as shown in this example:
Router (config)# config-register 0x2102
To break out of configuration mode, press Cntl and Z.
To save the blank configuration, issue the copy-running config-startup config command.
– See more at: https://supportforums.cisco.com/document/11856/resetting-router-factory-default-removing-startup-configuration-file#sthash.nyqBmH6Z.dpuf