[Day 5] 4. Cisco IOS (Internetwork Operating System)

• Cisco routers primarily use the CLI for configuration, as it provides direct interaction with the hardware, avoiding GUI overhead.

• Important Cisco Commands:

  • configure terminal: Opens global configuration mode.
  • hostname: Sets the router’s hostname.
  • enable secret: Sets an encrypted password for privileged mode access.
  • show version: Displays router details, including IOS version, memory sizes, and interfaces.
  • show flash: Lists the contents of the flash memory.
  • show running-config: Shows the current running configuration.
  • show startup-config: Displays the startup configuration stored in NVRAM.

• User Authentication:

  • Cisco routers use password protection at multiple levels (user-mode, privileged mode).
  • enable secret: Used to set a secure, encrypted password.

• Saving Configuration:

  • To save the current configuration to NVRAM, use the copy running-config startup-config command.
  • If not saved, all configurations will be lost after a power-off.

• Exec-timeout: Configures the time before the session times out due to inactivity.

Security Features in Cisco Routers:

• Password Encryption: Cisco uses encryption (e.g.,
  Copy

  service password-encryption

  ) to protect router passwords from being exposed.