Cisco CCNA Preparation · lesson 6 of 36 · 25 min
Cisco IOS Overview
Cisco IOS (Internetwork Operating System) is the software that runs on Cisco routers and switches. You interact with it through the CLI (Command Line Interface) via console cable, SSH, or Telnet. Understanding IOS modes is essential — the wrong mode means commands won’t work.
IOS Modes
Navigating Between Modes
Key shortcut
Ctrl+Z from any configuration mode jumps straight back to Privileged EXEC — faster than typing exit multiple times.
Helpful IOS Features
Flashcard Drill
Router> User EXEC mode — basic read-only commands. Router# Privileged EXEC mode — full show/debug access. Enter with: enable Router(config)# Global Configuration mode — device-wide changes. Enter with: configure terminal enable Command to enter Privileged EXEC from User EXEC. configure terminal Command to enter Global Configuration from Privileged EXEC. Ctrl+Z Returns directly to Privileged EXEC from any configuration mode. show running-config Displays the active configuration currently in RAM. copy running-config startup-config Saves the running config to NVRAM — persists after reboot. ? Context-sensitive help — shows available commands or options at any point. exit Moves up one mode level in the IOS hierarchy.
Knowledge Check
IOS Modes — 10 Questions
What prompt indicates you are in Privileged EXEC mode?
- Router>
- Router#
- Router(config)#
- Router(config-if)#
Answer: Router#
Router# is the Privileged EXEC prompt. Enter it with the enable command.
Which command enters Global Configuration mode from Privileged EXEC?
- enable
- configure terminal
- interface
- login
Answer: configure terminal
configure terminal (or conf t) moves from Privileged EXEC to Global Configuration.
You can make configuration changes from User EXEC mode.
- True
- False
Answer: False
User EXEC is read-only. Configuration changes require Global Configuration mode.
The keyboard shortcut _____ returns you directly to Privileged EXEC from any configuration mode.
Answer: Ctrl+Z
Ctrl+Z (or the end command) jumps directly to Privileged EXEC.
Where is the running configuration stored?
- NVRAM
- Flash
- RAM
- ROM
Answer: RAM
The running-config is stored in RAM — it is lost on reboot unless saved.
Which command saves the running configuration so it survives a reboot?
- write memory
- copy running-config startup-config
- save config
- Both A and B
Answer: Both A and B
Both write memory and copy running-config startup-config save the config to NVRAM.
What does typing ? at the CLI do?
- Exits the session
- Shows context-sensitive help
- Saves the configuration
- Reboots the device
Answer: Shows context-sensitive help
? provides context-sensitive help — shows available commands or options at the current position.
Which prompt indicates Interface Configuration mode?
- Router>
- Router#
- Router(config)#
- Router(config-if)#
Answer: Router(config-if)#
Router(config-if)# is the Interface Configuration mode prompt.
The startup-config is stored in NVRAM and persists after a reboot.
- True
- False
Answer: True
startup-config is in NVRAM — non-volatile memory that retains data without power.
To configure VTY lines for SSH access, you enter _____ configuration mode.
Answer: line
line vty 0 4 enters Line Configuration mode for VTY (SSH/Telnet) access.
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