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CCNA Lesson 4: Cisco IOS CLI Overview

May 10, 2025

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Jeremy's IT Lab - CCNA Lesson 4: Cisco IOS CLI

Introduction

  • Course designed to help pass the CCNA exam for free.
  • Includes quizzes and Anki flashcards for study aid.

Cisco IOS CLI Basics

  • Cisco IOS: Operating System for Cisco devices (not related to Apple's iOS).
  • CLI (Command-Line Interface): Used for configuring routers, switches, and firewalls.
  • CLI vs GUI: CLI preferred by most network engineers; GUIs like Cisco's ASDM exist but are not covered here.

Connecting to Cisco Devices

  • Console Port Connection:
    • Requires physical connection via console port on the device.
    • Ports: RJ45 and USB mini-B on devices like Cisco Catalyst switch.
    • Rollover Cable: Connects RJ45 and DB9 connector; often needs a USB adapter for laptops.
    • Cable Wiring: Pins connect in a specific rollover fashion (e.g., pin 1 to pin 8, etc.).

Accessing the CLI

  • Terminal Emulators: Example: PuTTY from putty.org.
    • Connect using serial connection settings.
    • Default settings: Speed 9600 bps, 8 data bits, 1 stop bit, no parity, no flow control.

CLI Navigation and Modes

  • User EXEC Mode: Limited access, indicated by >.
  • Privileged EXEC Mode: Full access to view configurations, indicated by #.
    • Entered via enable command.
  • Global Configuration Mode: Allows configuration changes, indicated by (config)#.
    • Enter using configure terminal or conf t.

CLI Shortcuts and Features

  • Tab Completion: Auto-completes commands.
  • Question Mark (?): List available commands or complete words.
    • Example: conf? for configure.
  • Command Shortcuts: Abbreviated commands can be used (e.g., en for enable).

Security: Passwords

  • Enable Password: Protects privileged EXEC mode but is shown in clear text in configurations.
  • Service Password-Encryption: Encrypts passwords in configuration files.
    • Limited security; passwords can be cracked.
  • Enable Secret: More secure, uses MD5 encryption, overrides enable password.
  • Removing Commands: Use no before a command to remove it.

Configuration Files

  • Running-Config: Currently active configuration.
  • Startup-Config: Loaded at device restart.
    • Save with commands like write, write memory, or copy running-config startup-config.

Quiz Questions (Review)

  • Types of cables, password issues, and secure password methods.

Supplementary Materials

  • Flash Cards: Link in description.
  • Packet Tracer Lab: Hands-on practice, highly recommended.

Conclusion

  • Importance of hands-on practice to master CLI.
  • Subscription and support through donations or using the Brave browser.

These notes summarize the main points from Jeremy's IT Lab CCNA Lesson 4 on configuring Cisco devices using the CLI. The lesson covers connecting to devices, navigating the CLI, using command shortcuts, and password security, concluding with a quiz to test comprehension.

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