Using the Command-Line Interface
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Using the Command-Line Interface

This chapter contains the following topics:

Information About Using the Command-Line Interface

This section describes the Cisco IOS command-line interface (CLI) and how to use it.

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.

When you start a session using Telnet, SSH, or console on the controller, 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 controller 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 controller 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.

 
Controller>

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.

 
Controller#

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.

 
Controller(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 controller.

VLAN configuration

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

 
Controller(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 controller startup configuration file.

Interface configuration

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

 
Controller(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.

 
Controller(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.

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 ActionPurpose
    Step 1 help


    Example: 
    Controller# help
     

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

     
    Step 2abbreviated-command-entry ?


    Example:
    Controller# di?
dir disable disconnect
     

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

     
    Step 3abbreviated-command-entry <Tab>


    Example:
    Controller# sh conf<tab>
Controller# show configuration
     

    Completes a partial command name.

     
    Step 4?


    Example:
    Controller> ?
     

    Lists all commands available for a particular command mode.

     
    Step 5command ?


    Example:
    Controller> show ?
     

    Lists the associated keywords for a command.

     
    Step 6command keyword ?


    Example:
    Controller(config)# cdp holdtime ?
  <10-255> Length of time (in sec) that receiver must keep this packet
     

    Lists the associated arguments for a keyword.

     

    Understanding Abbreviated Commands

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

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

    Controller# 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 controller.

    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 controller to recognize the 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.

    		 
    % Incomplete command.

    You did not enter all 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 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 controller 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.

    How to Use the CLI to Configure Features

    Configuring the Command History

    The software provides a history or record of commands that you have entered. The command history feature is particularly useful for recalling long or complex commands or entries, including access lists. You can customize this feature to suit your needs.

    Changing the Command History Buffer Size

    By default, the controller records ten command lines in its history buffer. You can alter this number for a current terminal session or for all sessions on a particular line. These procedures are optional.

    SUMMARY STEPS

      1.    terminal history [size number-of-lines]

      2.    history [size number-of-lines]


    DETAILED STEPS
       Command or ActionPurpose
      Step 1terminal history [size number-of-lines]


      Example: 
      Controller# terminal history size 200
       

      Changes the number of command lines that the controller records during the current terminal session in the privileged EXEC mode. You can configure the size from 0 through 256.

       
      Step 2history [size number-of-lines]


      Example:
      Controller(config)# history size 200
       

      Configures the number of command lines the controller records for all sessions on a particular line in the configuration mode. You can configure the size from 0 through 256.

       

      Recalling Commands

      To recall commands from the history buffer, perform one of the actions listed in this table. These actions are optional.


      Note

      The arrow keys function only on ANSI-compatible terminals such as VT100s.

      SUMMARY STEPS

        1.    Ctrl-P or use the up arrow key

        2.    Ctrl-N or use the down arrow key

        3.    show history


      DETAILED STEPS
         Command or ActionPurpose
        Step 1Ctrl-P or use the up arrow key
         

        Recalls commands in the history buffer, beginning with the most recent command. Repeat the key sequence to recall successively older commands.

         
        Step 2Ctrl-N or use the down arrow key
         

        Returns to more recent commands in the history buffer after recalling commands with Ctrl-P or the up arrow key. Repeat the key sequence to recall successively more recent commands.

         
        Step 3show history


        Example:
        Controller# show history
         

        Lists the last several commands that you just entered in privileged EXEC mode. The number of commands that appear is controlled by the setting of the terminal history global configuration command and the history line configuration command.

         

        Disabling the Command History Feature

        The command history feature is automatically enabled. You can disable it for the current terminal session or for the command line. These procedures are optional.

        SUMMARY STEPS

          1.    terminal no history

          2.    no history


        DETAILED STEPS
           Command or ActionPurpose
          Step 1 terminal no history


          Example: 
          Controller# terminal no history
           

          Disables the feature during the current terminal session in the privileged EXEC mode.

           
          Step 2no history


          Example:
          Controller(config)# no history
           

          Disables command history for the line in the configuration mode.

           

          Enabling and Disabling Editing Features

          Although enhanced editing mode is automatically enabled, you can disable it, reenable it, or configure a specific line to have enhanced editing. These procedures are optional.

          SUMMARY STEPS

            1.    no editing

            2.    terminal editing

            3.    editing


          DETAILED STEPS
             Command or ActionPurpose
            Step 1no editing


            Example: 
            Controller(config)# no editing
             

            Disables the enhanced editing mode.

             
            Step 2terminal editing


            Example:
            Controller# terminal editing
             

            Reenables the enhanced editing mode for the current terminal session in the privileged EXEC mode.

             
            Step 3editing


            Example:
            Controller(config)# editing
             

            Reconfigures a specific line to have enhanced editing mode.

             

            Editing Commands through Keystrokes

            The keystrokes help you to edit the command lines. These keystrokes are optional.


            Note

            The arrow keys function only on ANSI-compatible terminals such as VT100s.

            SUMMARY STEPS

              1.    Ctrl-B or use the left arrow key

              2.    Ctrl-F or use the right arrow key

              3.    Ctrl-A

              4.    Ctrl-E

              5.    Esc B

              6.    Esc F

              7.    Ctrl-T

              8.    Ctrl-Y

              9.    Esc Y

              10.    Delete or Backspace key

              11.    Ctrl-D

              12.    Ctrl-K

              13.    Ctrl-U or Ctrl-X

              14.    Ctrl-W

              15.    Esc D

              16.    Esc C

              17.    Esc L

              18.    Esc U

              19.    Ctrl-V or Esc Q

              20.    Return key

              21.    Space bar

              22.    Ctrl-L or Ctrl-R


            DETAILED STEPS
               Command or ActionPurpose
              Step 1Ctrl-B or use the left arrow key
               

              Moves the cursor back one character.

               
              Step 2Ctrl-F or use the right arrow key
               

              Moves the cursor forward one character.

               
              Step 3Ctrl-A
               

              Moves the cursor to the beginning of the command line.

               
              Step 4Ctrl-E
               

              Moves the cursor to the end of the command line.

               
              Step 5Esc B
               

              Moves the cursor back one word.

               
              Step 6Esc F
               

              Moves the cursor forward one word.

               
              Step 7Ctrl-T
               

              Transposes the character to the left of the cursor with the character located at the cursor.

               
              Step 8Ctrl-Y
               

              Recalls the most recent entry in the buffer.

              Recall commands from the buffer and paste them in the command line. The controller provides a buffer with the last ten items that you deleted.

               
              Step 9Esc Y
               

              Recalls the next buffer entry.

              The buffer contains only the last 10 items that you have deleted or cut. If you press Esc Y more than ten times, you cycle to the first buffer entry.

               
              Step 10Delete or Backspace key
               

              Erases the character to the left of the cursor.

               
              Step 11Ctrl-D
               

              Deletes the character at the cursor.

               
              Step 12Ctrl-K
               

              Deletes all characters from the cursor to the end of the command line.

               
              Step 13Ctrl-U or Ctrl-X
               

              Deletes all characters from the cursor to the beginning of the command line.

               
              Step 14Ctrl-W
               

              Deletes the word to the left of the cursor.

               
              Step 15Esc D
               

              Deletes from the cursor to the end of the word.

               
              Step 16Esc C
               

              Capitalizes at the cursor.

               
              Step 17Esc L
               

              Changes the word at the cursor to lowercase.

               
              Step 18Esc U
               

              Capitalizes letters from the cursor to the end of the word.

               
              Step 19Ctrl-V or Esc Q
               

              Designates a particular keystroke as an executable command, perhaps as a shortcut.

               
              Step 20Return key
               

              Scrolls down a line or screen on displays that are longer than the terminal screen can display.

              Note   

              The More prompt is used for any output that has more lines than can be displayed on the terminal screen, including show command output. You can use the Return and Space bar keystrokes whenever you see the More prompt.

               
              Step 21Space bar
               

              Scrolls down one screen.

               
              Step 22Ctrl-L or Ctrl-R
               

              Redisplays the current command line if the controller suddenly sends a message to your screen.

               

              Editing Command Lines That Wrap

              You can use a wraparound feature for commands that extend beyond a single line on the screen. When the cursor reaches the right margin, the command line shifts ten spaces to the left. You cannot see the first ten characters of the line, but you can scroll back and check the syntax at the beginning of the command. The keystroke actions are optional.

              To scroll back to the beginning of the command entry, press Ctrl-B or the left arrow key repeatedly. You can also press Ctrl-A to immediately move to the beginning of the line.


              Note

              The arrow keys function only on ANSI-compatible terminals such as VT100s.

              The following example shows how to wrap a command line that extend beyond a single line on the screen.

              SUMMARY STEPS

                1.    access-list

                2.    Ctrl-A

                3.    Return key


              DETAILED STEPS
                 Command or ActionPurpose
                Step 1access-list


                Example: 
                Controller(config)# access-list 101 permit tcp 10.15.22.25 255.255.255.0 10.15.22.35
Controller(config)# $ 101 permit tcp 10.15.22.25 255.255.255.0 10.15.22.35 255.25
Controller(config)# $t tcp 10.15.22.25 255.255.255.0 131.108.1.20 255.255.255.0 eq
Controller(config)# $15.22.25 255.255.255.0 10.15.22.35 255.255.255.0 eq 45
                 

                Displays the global configuration command entry that extends beyond one line.

                When the cursor first reaches the end of the line, the line is shifted ten spaces to the left and redisplayed. The dollar sign ($) shows that the line has been scrolled to the left. Each time the cursor reaches the end of the line, the line is again shifted ten spaces to the left.

                 
                Step 2Ctrl-A


                Example:
                Controller(config)# access-list 101 permit tcp 10.15.22.25 255.255.255.0 10.15.2$
                 

                Checks the complete syntax.

                The dollar sign ($) appears at the end of the line to show that the line has been scrolled to the right.

                 
                Step 3Return key
                 

                Execute the commands.

                The software assumes that you have a terminal screen that is 80 columns wide. If you have a different width, use the terminal width privileged EXEC command to set the width of your terminal.

                Use line wrapping with the command history feature to recall and modify previous complex command entries.

                 

                Searching and Filtering Output of show and more Commands

                You can search and filter the output for show and more commands. This is useful when you need to sort through large amounts of output or if you want to exclude output that you do not need to see. Using these commands is optional.

                SUMMARY STEPS

                  1.    {show | more} command | {begin | include | exclude} regular-expression


                DETAILED STEPS
                   Command or ActionPurpose
                  Step 1{show | more} command | {begin | include | exclude} regular-expression


                  Example: 
                  Controller# show interfaces | include protocol
Vlan1 is up, line protocol is up
Vlan10 is up, line protocol is down
GigabitEthernet1/0/1 is up, line protocol is down
GigabitEthernet1/0/2 is up, line protocol is up
                   

                  Searches and filters the output.

                  Expressions are case sensitive. For example, if you enter | exclude output, the lines that contain output are not displayed, but the lines that contain output appear.

                   

                  Accessing the CLI

                  You can access the CLI through a console connection, through Telnet, or by using the browser.

                  Accessing the CLI through a Console Connection or through Telnet

                  Before you can access the CLI, you must connect a terminal or a PC to the controller console or connect a PC to the Ethernet management port and then power on the controller, as described in the hardware installation guide that shipped with your controller.

                  If your controller is already configured, you can access the CLI through a local console connection or through a remote Telnet session, but your controller must first be configured for this type of access.

                  You can use one of these methods to establish a connection with the controller:

                  • Connect the controller console port to a management station or dial-up modem, or connect the Ethernet management port to a PC. For information about connecting to the console or Ethernet management port, see the controller hardware installation guide.

                  • Use any Telnet TCP/IP or encrypted Secure Shell (SSH) package from a remote management station. The controller must have network connectivity with the Telnet or SSH client, and the controller must have an enable secret password configured.

                    • The controller supports up to 16 simultaneous Telnet sessions. Changes made by one Telnet user are reflected in all other Telnet sessions.
                    • The controller supports up to five simultaneous secure SSH sessions.

                    After you connect through the console port, through the Ethernet management port, through a Telnet session or through an SSH session, the user EXEC prompt appears on the management station.