Cisco boot behavior: If you erase (delete) the startup configuration in NVRAM and then reboot the router, which mode will the device enter?

Introduction / Context:
Understanding Cisco IOS boot behavior is key when recovering devices or staging new configurations. The presence or absence of a startup configuration in NVRAM determines whether the interactive setup dialog is presented after boot.

Given Data / Assumptions:

• NVRAM holds the startup configuration file (startup-config).
• We have deleted this file (e.g., write erase or erase startup-config).
• The device otherwise boots normally (IOS image is valid).

Concept / Approach:
When no startup configuration exists, IOS prompts the user with the initial configuration dialog (setup mode) to help create a basic configuration. This is distinct from ROMMON (used when the image or boot variables are missing or corrupt) and distinct from normal EXEC modes that require a configuration to exist.

Step-by-Step Solution:

Verification / Alternative check:
Boot logs will show “System configuration dialog” prompt after reload. Creating and saving a new configuration prevents future prompts.

Why Other Options Are Wrong:

• Privileged EXEC and Global configuration modes are not entered automatically without a configuration.
• “NVRAM loaded mode” is not an IOS concept.
• ROMMON appears when the system cannot find/boot a valid IOS image, not when the startup-config is missing.

Common Pitfalls:
Confusing missing startup-config with image boot failure; forgetting to save the running configuration to NVRAM to avoid seeing setup mode in the future.

Final Answer:
Setup mode (initial configuration dialog)