The Cisco Internetwork Operating System (IOS) has an escalating set of network permissions as you move through the prompts or operating modes. When you first connect to a device you will be in User EXEC mode; then by issuing the enable command you are brought to Privileged EXEC mode. By issuing the configure terminal command you will be brought to Global Configuration mode.

Finally, by issuing one of any number of other commands you will be brought to an interface or sub-configuration mode.

The following figure graphically shows the escalation among these commands.


Regardless of the Cisco device that you are configuring, these standard but distinct modes or styles of the command prompt. You get to those command prompts using a cable, Secure Shell (SSH), or Telnet connection.

Each prompt serves a purpose, so you need to become familiar with them and understand what you can do at the prompts. The prompt itself is the indicator of the operating system mode, and it is the operating system mode that determines what commands you are allowed to use.