3 Modes of Cisco IOS

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Cisco routers and switches have an InterOperating System (IOS) operating system. The CLI is the primary user interface of the Cisco IOS for their router and switches. Command-line interface (CLI) supports different IOS modes:

  • User EXEC Mode
  • Privileged EXEC Mode
  • Global Configuration Mode
  • Setup Mode
  • ROM Monitor Mode
In addition, the Global configuration mode contains sub-configuration Modes. The figure below illustrates the Cisco IOS sub-configuration modes, also called extended configuration mode or specific configuration mode of the global configuration.
IOS Mode

User mode

User Mode, or User EXEC mode, is the first IOS mode a user enters and gets access to the router after logging in. We can recognize user mode by the > prompt after the name of the router/switch. The router’s default name is Router, and the switch’s is Switch. Using the hostname command, we can change the default hostname from Global Configuration mode. We will explain the command later in the coming articles.

The user mode is usually password-protected. You need a valid username and password to access this mode. This mode allows the user to execute only the basic commands, such as those that show the system’s status. The router cannot be configured or restarted from this mode. The figure below illustrates the user mode at CLI.

Privileged Mode

This mode is also known as enable mode or a privileged exec mode. Privileged exec mode allows a user to view extensive info about the router’s configuration and change some of the configuration parameters. The Privileged mode is also password protected. The user should enter the password to access this mode.

In the lab environment, it’s usually unprotected. You can use this mode by executing an enable command at user exec mode. We can list all available commands of this mode by entering a command-line interface (CLI). Most commands of this mode are one-time commands. Which shows the result and current status and clear counters on interfaces? We can enter common show commands from user exec or privileged exec modes. The Exec mode commands do not save across the reboot of the device. The figure-3 illustrates the Privileged mode of the router.

Global Configuration Mode

The configuration mode is only a temporary gateway IOS mode to get to extended configuration modes. Global configuration mode is used for configuring devices globally or to enter an element, like an interface or protocol-specific configuration mode. Access global configuration mode in the configure terminal command at privileged exec mode.

Global and extended (specific) configuration modes allow users to change the running configuration. By default, the running configuration is not stored across reboots, but you can save it to keep it across reboots. To save the running configuration, copy running-config startup-config from privileged EXEC mode commands. We have used three commands to return to privileged exec mode from global or specific configuration modes.

  • Ctrl + Z – This key combination works in all modes.
  • Exit – Only works in global configuration mode
  • The end command is the safest way to exit from global configuration or interface-specific modes.

Setup Mode

When a Cisco router is powered on, it first runs a POST test to ensure all hardware is working fine, and then the router tries to find the running configuration. If the router finds the configuration, it will load it. It will start the setup mode if it fails to find the configuration. The setup mode is a step-by-step process which helps you configure basic aspects of the router. In this mode, the router will ask questions about the first settings in a sequence for basic configuration values. Depending on your answers, the router will automatically build the initial configuration.

ROMMON Mode

ROMMON Mode, also known as ROM Monitor Mode, works if, during the boot process, a router does not find a valid IOS image and fails to load IOS in RAM. It would enter ROMMON mode. We can also access ROMMON Mode manually.

It is the diagnostic mode, just like the safe mode in Windows. By default, the router does not enter ROMMON Mode unless it fails to find the IOS image. To enter manually in ROMMON mode, execute the reload command from privileged exec mode and press the CTRL + C key combination or break during the first 60 seconds of startup. We can also use this mode to recover passwords. Prompt for this mode is rommon>