After the Cisco software has been installed, the device must be configured with the essential settings for proper network operations.
As you can see in the image above, if a saved startup configuration exists in NVRAM, the router uses it. Otherwise, if an active link is detected, the router may attempt to connect to a TFTP server by broadcasting the configuration request. If this approach fails (it usually fails), the router offers you the optional System Configuration Dialog (configuration wizard).
To view the running and startup configurations, use the “show running-configuration” and “show startup-configuration” commands, respectively.