1) User EXEC
2) Privileged EXEC
3) Global Configuration
4) Interface Configuration
5) Sub-Interface Configuration
6) Setup
7) ROMMON
User EXEC Mode
CISCO IOS always places the user in this mode. If configured, the IOS prompts the user to enter the password to access this mode.
Key Points -
-User EXEC Mode is having very limited commands that allow the user to view statistics and perform basic troubleshooting.
-User EXEC mode does not allow the user to change any of the settings.
-User EXEC mode is the EntrY point of the IOS. Other modes of the IOS can only be accessed through this mode.
Privileged EXEC Mode
Privileged EXEC mode can be accessed only from the user exec mode by executing the enable command.
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.
Key Points -
This mode is used for -
-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
NOTE- 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 it is clear from its name , this mode includes the commands that are used to configure the device.
Key Points -
-In Global Configuration 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.
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: -
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.
Key Points -
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.
Key Points -
-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.
The following table lists commands that are used to navigate the different modes of the IOS.
