Overview
This lecture covers the basics of configuring Cisco devices using the Cisco IOS CLI, different command modes, secure password configuration, saving device configurations, and essential CLI commands for the CCNA exam.
Cisco IOS and CLI Basics
- Cisco IOS is the operating system for Cisco devices (routers, switches, firewalls).
- CLI (Command-Line Interface) is used to configure Cisco devices.
- GUI (Graphical User Interface) exists but is not covered in this course.
- Connection to devices is initially via the console port using a rollover cable.
Connecting to Cisco Devices
- Use a rollover cable (RJ45 to DB9) or USB mini-B, plus a USB adapter if needed.
- Terminal emulator software like PuTTY is used to access the CLI.
- Default serial settings: speed 9600 bps, 8 data bits, 1 stop bit, no parity, no flow control.
Cisco CLI Modes
- User EXEC mode: limited access, indicated by
>.
- Privileged EXEC mode: more access (viewing/saving config), indicated by
#, entered with enable.
- Global Configuration mode: used to make configuration changes, shows
(config)#, entered with configure terminal or conf t.
CLI Shortcuts and Help
- Tab completes commands; partial commands can be used if unambiguous.
? shows available commands or options.- Use
do before privileged EXEC commands in configuration modes.
Password Protection and Encryption
- Use
enable password <password> in global config mode to set privileged EXEC mode password (case-sensitive).
service password-encryption encrypts passwords in configuration but uses weak encryption (type 7).enable secret <password> sets a more secure, MD5-encrypted (type 5) password for privileged EXEC mode; overrides enable password if both set.no <command> removes a configuration command.
Viewing and Saving Configurations
show running-config shows the current (active) configuration.show startup-config shows the saved configuration loaded at reboot.- Save config with
write, write memory, or copy running-config startup-config.
Key Terms & Definitions
- Cisco IOS — The operating system used on Cisco devices.
- CLI — Command-Line Interface for device configuration.
- User EXEC mode — Initial, limited access CLI mode (
>).
- Privileged EXEC mode — Higher-level access, allows more commands (
#).
- Global Configuration mode — Mode for making configuration changes (
(config)#).
- Rollover cable — Special cable for console port connection.
- Enable password — Plain-text password for privileged EXEC mode.
- Enable secret — MD5-encrypted password for privileged EXEC mode.
- Running-config — The active configuration in RAM.
- Startup-config — The saved configuration loaded at boot.
- Service password-encryption — Command to encrypt passwords in config files.
Action Items / Next Steps
- Download and review Anki flashcards from the provided link.
- Complete the Packet Tracer lab for hands-on CLI practice.
- Review full-length command versions and practice using shortcuts in labs.