Using the Command-Line Interface

Information About Using the Command-Line Interface


Note

Search options on the GUI and CLI are case sensitive.

Command Modes

The Cisco IOS user interface is divided into many different modes. The commands available to you depend on which mode you are currently in. Enter a question mark (?) at the system prompt to obtain a list of commands available for each command mode.

You can start a CLI session through a console connection, through Telnet, an SSH, or by using the browser.

When you start a session, you begin in user mode, often called user EXEC mode. Only a limited subset of the commands are available in user EXEC mode. For example, most of the user EXEC commands are one-time commands, such as show commands, which show the current configuration status, and clear commands, which clear counters or interfaces. The user EXEC commands are not saved when the device reboots.

To have access to all commands, you must enter privileged EXEC mode. Normally, you must enter a password to enter privileged EXEC mode. From this mode, you can enter any privileged EXEC command or enter global configuration mode.

Using the configuration modes (global, interface, and line), you can make changes to the running configuration. If you save the configuration, these commands are stored and used when the device reboots. To access the various configuration modes, you must start at global configuration mode. From global configuration mode, you can enter interface configuration mode and line configuration mode .

This table describes the main command modes, how to access each one, the prompt you see in that mode, and how to exit the mode.

Table 1. Command Mode Summary

Mode

Access Method

Prompt

Exit Method

About This Mode

User EXEC

Begin a session using Telnet, SSH, or console. 


Device>

Enter logout or quit .

Use this mode to

  • Change terminal settings.

  • Perform basic tests.

  • Display system information.

Privileged EXEC

While in user EXEC mode, enter the enable command. 


Device#

Enter disable to exit.

Use this mode to verify commands that you have entered. Use a password to protect access to this mode.

Global configuration

While in privileged EXEC mode, enter the configure command. 


Device(config)#

To exit to privileged EXEC mode, enter exit or end , or press Ctrl-Z.

Use this mode to configure parameters that apply to the entire device.

VLAN configuration

While in global configuration mode, enter the vlan vlan-id command. 


Device(config-vlan)#

To exit to global configuration mode, enter the exit command.

To return to privileged EXEC mode, press Ctrl-Z or enter end .

Use this mode to configure VLAN parameters. When VTP mode is transparent, you can create extended-range VLANs (VLAN IDs greater than 1005) and save configurations in the device startup configuration file.

Interface configuration

While in global configuration mode, enter the interface command (with a specific interface). 


Device(config-if)#

To exit to global configuration mode, enter exit .

To return to privileged EXEC mode, press Ctrl-Z or enter end .

Use this mode to configure parameters for the Ethernet ports.

Line configuration

While in global configuration mode, specify a line with the line vty or line console command. 


Device(config-line)#

To exit to global configuration mode, enter exit .

To return to privileged EXEC mode, press Ctrl-Z or enter end .

Use this mode to configure parameters for the terminal line.

Understanding Abbreviated Commands

You need to enter only enough characters for the device to recognize the command as unique.

This example shows how to enter the show configuration privileged EXEC command in an abbreviated form: 


Device# show conf

No and Default Forms of Commands

Almost every configuration command also has a no form. In general, use the no form to disable a feature or function or reverse the action of a command. For example, the no shutdown interface configuration command reverses the shutdown of an interface. Use the command without the keyword no to reenable a disabled feature or to enable a feature that is disabled by default.

Configuration commands can also have a default form. The default form of a command returns the command setting to its default. Most commands are disabled by default, so the default form is the same as the no form. However, some commands are enabled by default and have variables set to certain default values. In these cases, the default command enables the command and sets variables to their default values.

CLI Error Messages

This table lists some error messages that you might encounter while using the CLI to configure your device.

Table 2. Common CLI Error Messages

Error Message

Meaning

How to Get Help

 
% Ambiguous command: "show con"

You did not enter enough characters for your device to recognize the command.

Reenter the command followed by a question mark (?) without any space between the command and the question mark.

The possible keywords that you can enter with the command appear.

 
% Incomplete command.

You did not enter all of the keywords or values required by this command.

Reenter the command followed by a question mark (?) with a space between the command and the question mark.

The possible keywords that you can enter with the command appear.

 
% Invalid input detected at ‘^’ marker.

You entered the command incorrectly. The caret (^) marks the point of the error.

Enter a question mark (?) to display all of the commands that are available in this command mode.

The possible keywords that you can enter with the command appear.

Configuration Logging

You can log and view changes to the device configuration. You can use the Configuration Change Logging and Notification feature to track changes on a per-session and per-user basis. The logger tracks each configuration command that is applied, the user who entered the command, the time that the command was entered, and the parser return code for the command. This feature includes a mechanism for asynchronous notification to registered applications whenever the configuration changes. You can choose to have the notifications sent to the syslog.


Note

Only CLI or HTTP changes are logged.

Using the Help System

You can enter a question mark (?) at the system prompt to display a list of commands available for each command mode. You can also obtain a list of associated keywords and arguments for any command.

SUMMARY STEPS

  1. help
  2. abbreviated-command-entry ?
  3. abbreviated-command-entry <Tab>
  4. ?
  5. command ?
  6. command keyword ?

DETAILED STEPS

  Command or Action Purpose

Step 1

help

Example:

Device# help

Obtains a brief description of the help system in any command mode.

Step 2

abbreviated-command-entry ?

Example:

Device# di?
dir disable disconnect

Obtains a list of commands that begin with a particular character string.

Step 3

abbreviated-command-entry <Tab>

Example:

Device# sh conf<tab>
Device# show configuration

Completes a partial command name.

Step 4

?

Example:

Device> ?

Lists all commands available for a particular command mode.

Step 5

command ?

Example:

Device> show ?

Lists the associated keywords for a command.

Step 6

command keyword ?

Example:

Device(config)# wireless management ?
certificate  Configure certificate details
interface    Select an interface to configure
transfer     Active transfer profiles
trustpoint   Select a trustpoint to configure

Lists the associated arguments for a keyword.