Saving configuration to NVRAM: Which exact Cisco IOS command (entered from privileged EXEC) saves the current running configuration in RAM to the startup configuration in NVRAM?

Introduction / Context:
On Cisco IOS, configuration changes are made to the running configuration in RAM. To ensure those changes persist across reloads, you must copy the running configuration to the startup configuration stored in NVRAM. Recognizing the correct command and mode prevents accidental loss of settings after a reboot.

Given Data / Assumptions:

• We are working on a Cisco router.
• The goal is to save the running configuration so it is retained after a reload.
• The question emphasizes the proper command and prompt context.

Concept / Approach:

Persistence is achieved with the IOS copy command. In privileged EXEC mode (Router#), the canonical long form is copy running-config startup-config. IOS also permits supported abbreviations, commonly written as copy run startup, which is functionally identical. The operation writes the configuration snapshot into NVRAM for the next boot.

Step-by-Step Solution:

Verification / Alternative check:

Reload the router (or issue show startup-config) to confirm the saved configuration matches the intended changes. The running and startup configurations should align after a successful copy.

Why Other Options Are Wrong:

Option A is not valid IOS syntax.

Option B reverses the direction (that would overwrite the running config from startup, not save changes).

Option C shows the long form but at the wrong prompt (Router(config)#); the command is not executed from global configuration mode.

Common Pitfalls:

Forgetting to save after changes; misreading the direction of copy; assuming write memory happens automatically (on modern IOS you can use write memory, but it must still be invoked).

Final Answer:

Router#copy run startup