When the CLI is launched, it begins in Standard mode. This is the most restrictive mode and only has commands to query a restricted set of state information. You cannot take any actions that would directly affect the system, nor can you change any configuration.
The enable command moves you to
Enable mode. This has commands to view all state information, and take certain kinds of actions like rebooting the system, but does not allow any configuration to be changed. Its commands are a superset of those in Standard mode. Enter
disable to exit
Enable mode.
The configure terminal command moves you to
Configuration mode. This has a full unrestricted set of commands to view anything, take any action, or change any configuration. Its commands are a superset of those in
Enable mode. Enter
exit to leave
Configuration mode.
Some commands have a prefix mode; that is, when you enter a keyword, you enter a mode for that configuration. For example:
When in the prefix mode, you can only make configurations for that command set and typing
? (question mark) shows you only the options for those configurations. To leave the prefix mode, type
exit.