Cisco IOS Cookbook, 2nd Edition

Clearing the Startup Configuration

Problem

You want to clear an old configuration out of your router and return it to a factory default configuration.

Solution

You can delete the current startup configuration files and return the router to its factory default settings with the erase nvram: command:

Router1#erase nvram:
Erasing the nvram filesystem will remove all files! Continue? [confirm] <enter>
[OK]
Erase of nvram: complete
Router1#reload

System configuration has been modified. Save? [yes/no]: no
Proceed with reload? [confirm]<enter>

You can achieve the same result with the erase startup-config command:

Router1#erase startup-config 
Erasing the nvram filesystem will remove all files! Continue? [confirm] <enter>
[OK]
Erase of nvram: complete
Router1#reload
Proceed with reload? [confirm]<enter>

Discussion

Before you redeploy an old router that you have previously used for some other purpose, it is a good idea to completely erase the old configuration. This ensures that the router starts with a clean configuration. However, if you did this on a production router, it would wipe out the configuration and leave it with all of its interfaces down. Fortunately, completely deleting your configuration requires two steps: erasing the startup configuration file, followed by a reload.

After you erase your startup configuration file and reload the router, it will enter its configuration dialog mode. Most experienced Cisco engineers prefer to skip this mode:

--- System Configuration Dialog --- Would ...