part 2

• Shell


  The user interface that allows users to request specific tasks from the computer. These requests can be made either through the CLI or GUI interfaces.
• Kernel


  Communicates between the hardware and software of a computer and manages how hardware resources are used to meet software requirements.
• Hardware


  The physical part of a computer including underlying electronics.
• GUI

  A GUI allows the user to interact with the system using an environment of graphical icons, menus, and windows.
• A GUI is more user-friendly and requires less knowledge of the underlying command structure that controls the system.
• Examples of these are:

  • Windows, macOS, Linux KDE, Apple iOS and Android.
• GUIs can fail, crash, or simply not operate as specified. For these reasons, network devices are typically accessed through a CLI.
• Purpose of a PC operating system

  Enable a user to use a mouse to make selections and run programs, enter text and text-based commands
• Purpose of a CLI-based network operating system

  Enable a network technician to use a keyboard to run CLI-based network programs, enter text and text-based commands, view output on a monitor
• Console


  A physical management port used to access a device in order to provide maintenance, such as performing the initial configurations.
• Secure Shell (SSH)


  Establishes a secure remote CLI connection to a device, through a virtual interface, over a network. (Note: This is the recommended method for remotely connecting to a device.)
• Telnet


  Establishes an insecure remote CLI connection to a device over the network. (Note: User authentication, passwords and commands are sent over the network in plaintext.)
• Terminal emulation programs

  Used to connect to a network device by either a console port or by an SSH/Telnet connection.
• Examples of terminal emulation programs

  • PuTTY, Tera Term and SecureCRT.
• User EXEC Mode


  Allows access to only a limited number of basic monitoring commands. Identified by the CLI prompt that ends with the > symbol.
• Privileged EXEC Mode


  Allows access to all commands and features. Identified by the CLI prompt that ends with the # symbol.
• Global Configuration Mode


  Used to access configuration options on the device.
• Line Configuration Mode


  Used to configure console, SSH, Telnet or AUX access.
• Interface Configuration Mode


  Used to configure a switch port or router interface.
• Navigation Between IOS Modes

  1. To move from user EXEC mode to privilege EXEC mode, use the enable command.

  2. To move in and out of global configuration mode, use the configure terminal command. To return to privilege EXEC mode, use the exit command.

  3. To move in and out of line configuration mode, use the line command followed by the management line type. To return to global configuration mode, use the exit command.

  4. To move out of any subconfiguration mode to get back to global configuration mode, use the exit command. To return to privilege EXEC mode, use the end command or key combination Ctrl +Z.

  5. To move directly from one subconfiguration mode to another, type in the desired subconfiguration mode command.
• Keyword


  A specific parameter defined in the operating system
• Argument


  A value or variable defined by the user
• Boldface text indicates commands and keywords that are entered as shown. Italic text indicates an argument for which the user provides the value.
• Context-sensitive help


  Enables you to quickly find answers to which commands are available in each command mode, which commands start with specific characters or group of characters, and which arguments and keywords are available to particular commands.
• Command syntax check


  Verifies that a valid command was entered by the user. If the interpreter cannot understand the command being entered, it will provide feedback describing what is wrong with the command.
• Commands and keywords can be shortened to the minimum number of characters that identify a unique selection.
• Hot keys and shortcuts

  • Tab
  • Backspace
  • Left Arrow or Ctrl+B
  • Right Arrow or Ctrl+F
  • Up Arrow or Ctrl+P
• Hot keys and shortcuts

  Features that make configuring, monitoring, and troubleshooting easier in the IOS CLI
• Command shortening


  Commands and keywords can be shortened to the minimum number of characters that identify a unique selection
• Command shortening


  • configure can be shortened to conf
• Using command shortening


  1. Router#con

  2. Router#con?

  3. Router#conf t
• Keystrokes to enhance command line editing


  • Tab
  • Backspace
  • Left Arrow or Ctrl+B
  • Right Arrow or Ctrl+F
  • Up Arrow or Ctrl+P
• Keystrokes when "--More--" prompt is displayed


  • Enter Key
  • Space Bar
  • Any other key
• Commands to exit out of an operation

  • Ctrl-C
  • Ctrl-Z
  • Ctrl-Shift-6
• The first configuration command on any device should be to give it a unique hostname
• Device naming guidelines


  • Start with a letter
  • Contain no spaces
  • End with a letter or digit
  • Use only letters, digits, and dashes
  • Be less than 64 characters in length
• Password guidelines


  • Use passwords that are more than eight characters in length
  • Use a combination of upper and lowercase letters, numbers, special characters, and/or numeric sequences
  • Avoid using the same password for all devices
  • Do not use common words because they are easily guessed
• Securing user EXEC mode access

  1. Enter line console configuration mode

  2. Specify the user EXEC mode password

  3. Enable user EXEC access
• Securing privileged EXEC mode access


  1. Enter global configuration mode

  2. Use the enable secret password command
• Securing VTY line access

  1. Enter line VTY configuration mode

  2. Specify the VTY password

  3. Enable VTY access