Notes on Cisco IOS and Command Modes

Overview of Cisco IOS and Command Modes

  • CISCO IOS Functionality
    • Used for configuration, monitoring, and troubleshooting.
    • Key features: Command Line Interface (CLI), configuration commands, and operational modes.

Basic Objectives of the Lecture

  • Operation of CISCO IOS using CLI commands.
  • Examples in Cisco Packet Tracer.

Cisco IOS Operating Modes

  • Different Command Modes
    • Each mode has a specific operational domain and command set.
    • Hierarchical structure of modes, each level can have its own password for access control.
Types of Modes

  1. User EXEC Mode

    • Limited set of commands (viewing commands).
    • Prompt: Router>
    • Example commands: ping, show (limited).

  2. Privileged EXEC Mode (Enable Mode)

    • Access to the full command set.
    • Prompt: Router#
    • Key commands: debug, reload, configure.

  3. Global Configuration Mode

    • Commands affect the router globally.
    • Prompt: Router(config)#
    • Example commands include hostname, enable secret, ip route, interface.

  4. Specific Configuration Modes

    • Interface Configuration Mode: Configuration commands for interfaces.
      • Example: Router(config-if)# ip address.
    • Routing Configuration Mode: Commands for setting up routing protocols.
      • Example: Router(config-router)# network.

  5. Line Configuration Mode

    • Commands for console and virtual terminal lines.
    • Example: Router(config-line)# password.

Command Syntax

  • Commands are case-insensitive but typically written in lower case.
  • Format: command [key-words] [arguments]
    • This allows for the specification of particular parameters or user-defined values.
CLI Help Features
  • Context-Sensitive Help: Use ? after command to see options.
  • Command Syntax Check: Automatically checks if the command is correct.
  • Keyboard Shortcuts:
    • Tab: Completes command.
    • Ctrl+Z: Exits configuration mode.
    • Up-arrow: Recalls previous commands.

Examination Commands for Routers

  • Show Commands
    • show version: Displays IOS version and router information.
    • show interfaces: Displays status and configuration of interfaces.
    • show running-config: Displays current configuration in RAM.
    • show startup-config: Displays configuration stored in NVRAM.

Examples of CLI Commands

  1. Viewing Version:

    • Router> enable -> Router# show version

  2. Change Router's Hostname:

    • Router> enable -> Router# configure terminal -> Router(config)# hostname R1

  3. Save Configuration:

    • R1# copy running-config startup-config

  4. Set Console Password:

    • R1(config)# line console 0 -> R1(config-line)# password pass1 -> R1(config-line)# login

  5. Set Password for vty Lines:

    • R1(config)# line vty 0 15 -> R1(config-line)# password pass2-> R1(config-line)# login

Cisco Packet Tracer

  • Simulation tool to practice Cisco CLI commands.
  • Modules include Router configurations and interface settings.
  • Displays real-time status of configurations.

Encryption of Passwords

  • Setting Enable Secret:
    • Use enable secret pass3 for better security.
  • Service Password Encryption:
    • service password-encryption to encrypt all plain text passwords.

Setting Banners

  • To set Message of the Day (motd):
    • R1(config)# banner motd #Welcome to the network!#

Conclusion

  • Understanding modes and commands is crucial for effective router management and configuration in Cisco IOS. Practice using these commands in Cisco Packet Tracer for enhanced learning and familiarity.