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Cisco IOS software overview

ICND1 and ICND2 break down


Cisco IOS software is the embedded software architecture in all Cisco devices and is also the operating system of Cisco Catalyst switches.

The Cisco IOS Software command-line interface (CLI) is used by network administrators to monitor and configure Cisco devices. You access the CLI by establishing a console connection or a Telnet connect connection to the Cisco devices. Log in to the Cisco device brings up a CLI window, where you are put into user EXEC mode by default and the prompt sign is ">". The command exit close the session from the user EXEC mode.

The Cisco IOS software CLI have very handy help features.

  • command avialability help: enter the ? (question mark) command at the user EXEC mode or privileged EXEC mode will reveal commands that available at that EXEC level.

  • word help: Enter an incomplete command followed by a ? (without any space between) will display a list of available commands that start with the characters that you entered.  

  • word auto-complete: Enter an incomplete command, then press TAB key will automatically complete the command for you, provide that only one command exists which start with the characters that you entered.

  • command syntax help: Enter a command followed by a space then ? will display a list of the available command options supported by the command that you entered.

The following is the CLI help features demonstration on a Cisco 2960-24TT switch:

 ----------------------------------------------------Demo Start--------------------------------------------------------

Press RETURN to get started!




User Access Verification

Password:

Switch>?
Exec commands:
  <1-99>      Session number to resume
  connect     Open a terminal connection
  disconnect  Disconnect an existing network connection
  enable      Turn on privileged commands
  exit        Exit from the EXEC
  logout      Exit from the EXEC
  ping        Send echo messages
  resume      Resume an active network connection
  show        Show running system information
  telnet      Open a telnet connection
  terminal    Set terminal line parameters
  traceroute  Trace route to destination
Switch>sh?
show
Switch>show ?
  cdp                CDP information
  clock              Display the system clock
  dtp                DTP information
  etherchannel       EtherChannel information
  flash:             display information about flash: file system
  history            Display the session command history
  interfaces         Interface status and configuration
  ip                 IP information
  mac-address-table  MAC forwarding table
  sessions           Information about Telnet connections
  tcp                Status of TCP connections
  terminal           Display terminal configuration parameters
  users              Display information about terminal lines
  version            System hardware and software status
  vlan               VTP VLAN status
  vtp                VTP information
Switch>show ip ?
  arp        IP ARP table
  interface  IP interface status and configuration
Switch>show ip interface ?  Vlan   Catalyst Vlans
  brief  Brief summary of IP status and configuration
  <cr>
Switch>show ip interface
Vlan1 is administratively down, line protocol is down
  Internet protocol processing disabled
Switch>enable
Switch#?
Exec commands:
  <1-99>      Session number to resume
  clear       Reset functions
  clock       Manage the system clock
  configure   Enter configuration mode
  connect     Open a terminal connection
  copy        Copy from one file to another
  debug       Debugging functions (see also 'undebug')
  delete      Delete a file
  dir         List files on a filesystem
  disable     Turn off privileged commands
  disconnect  Disconnect an existing network connection
  enable      Turn on privileged commands
  erase       Erase a filesystem
  exit        Exit from the EXEC
  logout      Exit from the EXEC
  more        Display the contents of a file
  no          Disable debugging informations
  ping        Send echo messages
  reload      Halt and perform a cold restart
  resume      Resume an active network connection
  setup       Run the SETUP command facility
 --More--

----------------------------------------------------Demo end--------------------------------------------------------




Note two points.

Firstly, in the following lines:

Switch>show ip interface ?  Vlan   Catalyst Vlans
  brief  Brief summary of IP status and configuration
  <cr>
where <cr> means press ENTER key.

Secondly,

--More-- means there are more lines to be displayed, press ENTER key to show one line, press SPACE key to show all lines.