The two primary modes of operation are user EXEC mode and privileged EXEC mode. As a security feature, the Cisco IOS software separates the EXEC sessions into two levels of access. As shown in the figure, the privileged EXEC mode has a higher level of authority in what it allows the user to do with the device.
User EXEC Mode
The user EXEC mode has limited capabilities but is useful for some basic operations. The user EXEC mode is at the most basic level of the modal hierarchical structure. This mode is the first mode encountered upon entrance into the CLI of an IOS device.
The user EXEC mode allows only a limited number of basic monitoring commands. This is often referred to as view-only mode. The user EXEC level does not allow the execution of any commands that might change the configuration of the device.
By default, there is no authentication required to access the user EXEC mode from the console. However, it is a good practice to ensure that authentication is configured during the initial configuration.
The user EXEC mode is identified by the CLI prompt that ends with the > symbol. This is an example that shows the > symbol in the prompt:
Privileged EXEC Mode
The execution of configuration and management commands requires that the network administrator use the privileged EXEC mode or a more specific mode in the hierarchy. This means that a user must enter user EXEC mode first, and from there, access privileged EXEC mode.
The privileged EXEC mode can be identified by the prompt ending with the # symbol.
By default, privileged EXEC mode does not require authentication. It is a good practice to ensure that authentication is configured.
Global configuration mode and all other more specific configuration modes can only be reached from the privileged EXEC mode. In a later section of this chapter, we will examine device configuration and some of the configuration modes.