IOS command modes include user EXEC mode, privileged EXEC mode, global configuration mode, and submodes. User EXEC mode has basic commands and the > prompt. Privileged EXEC mode requires enable access and has # prompt. Global configuration mode is entered with configure terminal and configures devices with (config) prompt. Submodes further configure resources like interfaces with (config-if) prompt.

1. IOS command modes
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2. User EXEC mode commands
 Initially, a user logs into the User Exec mode. This is the mode with the least number of
commands. You can get a list of all available commands by typing the character "?".

3.  As you can see, most of the commands available are used to show
statistics and perform some basic troubleshooting.
 The prompt on the left side of the screen always displays the
device hostname (R1 in this case), followed by the character >.
 All commands can be abbreviated to their first letters of the
command name.
 For example, you can abbreviate ping by typing pin, because no
other command in the User EXEC mode IOS mode begins with
these letters.

4. Privileged EXEC mode commands
 This IOS mode is also called enable mode because you must
enter the enable command from a user EXEC mode, if you want
to access this mode.
 You can use more commands in the privileged EXEC mode than
you were able to use in the user EXEC mode.
 You can save a device configuration or reload a device in this
mode.
 You can also enter a third mode, the configuration mode.
 An access to this mode can be protected by a password.
 The prompt for this mode shows # after the device hostname.

6. Global configuration mode commands
 To change a device configuration, you need to enter the global
configuration mode.
 This mode can be accessed by typing configure terminal (or conf t,
the abbreviated version of the command) from the enable mode.
 The prompt for this mode is hostname(config).
 Global configuration mode commands are used to configure a
device.
 You can set a hostname, configure authentication, set an IP address
for an interface, etc.
 From this mode you can also access sub modes, for example the
interface mode, from where you can configure interface options.
 You can get back to a privileged EXEC mode by typing
the end command. You can also type CTRL + C to exit the
configuration mode.

9. Submode commands
 A global configuration mode contains many sub modes.
 For example, if you want to configure an interface you have to enter that
interface configuration mode. Each submode contains only commands
that pertain to the resource that is being configured.
 To enter the interface configuration mode you need to specify which
interface you would like to configure.
 This is done by using the interface
INTERFACE_TYPE/INTERFACE_NUMBER global configuration
command, where INTERFACE_TYPE represents the type of an interface
(Ethernet, Fast Ethernet, Serial...)
and INTERFACE_NUMBER represents the interface number, since
Cisco devices usually have more than one physical interface.
 Once inside the interface configuration mode, you can get a list of
available commands by typing the "?" character. Each submode has its
own prompt.
 Notice how the command prompt was changed to HOSTNAME(config-
if).