This tutorial explains what the Cisco IOS modes are and how they work in detail. Learn the Cisco modes and the commands that are used to navigate and access them.
Cisco IOS software allows us to control the Cisco device on which it runs. IOS software contains several commands to configure and control Cisco devices. Not all these commands are the same. Some commands only provide information while others allow us to configure and control a particular feature, or a specific area of the device, or the entire device.
Based on how IOS commands affect the device, they are organized into the modes. An IOS mode is a group of commands that are used to configure similar features or to control a particular area of the device. An IOS mode is also known as the IOS access mode or the IOS commands mode.
There are five IOS modes: - user EXEC mode, privileged EXEC mode, global configuration mode, setup mode, and ROM Monitor mode.
The first three modes are used to view current settings and configure new settings or modify existing settings. The next two modes are used to set up the initial device configuration and troubleshoot the device in an emergency, respectively.
Let's understand each mode in detail.
User EXEC Mode
This is the first mode of the IOS. No matter how a user accesses the IOS, the IOS always places the user in this mode. If configured, the IOS prompts the user to enter the password to access this mode.
This mode has very limited commands that allow the user to view statistics and perform basic troubleshooting. This mode does not allow the user to change any of the settings. This mode is the starting (or entry) point of the IOS. Other modes of the IOS can only be accessed through this mode.
Privileged EXEC Mode
This is the second mode of the IOS. This mode can be accessed only from the user exec mode by executing the enable command. Since the enable command is used to access this mode, this mode is also known as the enable mode.
To close this mode or to return into the user exec mode, use the exit command or the end command.
As the name suggests, this mode includes privileged or powerful commands. This mode is usually used for the following purposes: -
- To view, save and erase device configuration
- To take the backup of the current device configuration
- To restore the configuration from backup
- To install a new IOS image file
- To debug or troubleshoot the device
- To restart or reload the device
Although this mode allows the user to manage device configuration and IOS image files, it does not allow the user to change the device configuration. A user can change device configuration only from the configuration mode.
Global configuration mode
As the name suggests, this mode includes the commands that are used to configure the device. From this mode, a user can not only configure new settings but can also change, update or delete existing settings.
To enter this mode, use the 'configure terminal' command from the privileged-exec mode. To exit from this mode, you can use the 'end' or the 'exit' commands. You can also press the CTRL + Z key combinations.
The following image shows how to navigate between the user exec mode, privileged exec mode and the global configuration mode.
Of all available modes, this mode has the largest number of commands. To organize these commands more effectively, this mode groups similar commands into sub-configuration modes.
Sub-configuration modes are IOS specific. Cisco makes several flavors of IOS software. A sub-configuration mode available in one flavor of IOS may or may not be available in other flavors of IOS.
The following table lists some of the most common sub-configuration modes that are commonly available across all flavors of the IOS.
| Sub-configuration mode | Contains commands that are used to: - |
| Interface configuration mode | Configure a physical interface of the device |
| Sub-interface configuration mode | Configure virtual interfaces |
| Routing protocol configuration mode | Configure a routing protocol |
| IP access list configuration mode | Configure in-built security feature of the IOS |
| Line configuration mode | Configure access modes of the IOS |
Setup Mode
When we power-on the IOS operated device, the IOS looks for the device configuration. If it does not find a valid configuration, it places the user in this mode. This mode allows the user to configure the initial device configuration.
This mode presents a text-based wizard that asks questions about initial settings in the sequence. Based on the answers provided by the user, the IOS automatically builds the initial configuration.
ROMMON Mode
During the boot process, the IOS image file is loaded into the RAM. If the IOS image file is missing or corrupt, the device automatically enters this mode. This mode allows the user to troubleshoot the IOS.
In this mode, the user can select a different IOS image file to boot the device or load a new IOS image file from the TFTP server.
The following image shows how all IOS modes work together.
Cisco IOS modes navigation
The following table lists commands that are used to navigate the different modes of the IOS.
| Mode | Prompt | Command to enter | Command to exit |
| User EXEC | Router > | Default mode after booting. Login with the password, if configured. | Use the exit command |
| Privileged EXEC | Router # | Use the enable command from the user exec mode | Use the exit or end command |
| Global Configuration | Router(config)# | Use the 'configure terminal' command from the privileged exec mode | Use the exit command |
| Interface Configuration | Router(config-if)# | Use the 'interface type number' command from the global configuration mode | Use the exit command to return in global configuration mode |
| Sub-Interface Configuration | Router(config-subif) | Use the 'interface type sub interface number' command from the global configuration mode or the interface configure mode. | Use the exit command to return in the previous mode. Use the end command to return in the privileged exec mode. |
| Setup | Parameter[Parameter value]: | After booting, the IOS automatically starts this mode, if it does not detect the running configuration. | Press CTRL+C to abort. Type Yes to save the configuration, or No to exit without saving when asked at the end of the setup program. |
| ROMMON | ROMMON> | Starts automatically if functional IOS is missing. To start manually, Press the CTRL + C key during the first 60 seconds of the booting process | Use the exit command. |
That's all from this part. In the next part of this tutorial, we will learn how to take the backup of the IOS and restore it from the backup when it is required. If you like this tutorial, please don't forget to share it with friends through your favorite social network.
