what is the effect of using the router# copy running-config startup-config command on a router?

The copy running-config startup-config command saves the current active router configuration to non-volatile memory. This ensures settings persist after a reboot or power cycle.

Command Breakdown

Entered in privileged EXEC mode (router# prompt) on Cisco IOS devices, it copies the running-config (volatile RAM storage) to startup-config (NVRAM storage). Running-config reflects live changes like interface tweaks or ACLs, but without this save, they'd vanish on reload.

• No impact on ROM : Read-only memory stays untouched.

• No RAM alteration : Source config in RAM remains identical.

• Flash unaffected : Typically holds IOS images, not configs.

• NVRAM updated : Startup-config file overwrites here, preserving your work.

Why It Matters

Imagine tweaking VLANs during a busy shift—skip this, and reboot wipes everything back to factory defaults, causing outages. It's like hitting "Save" in a game before quitting; pros do wr (alias for brevity) habitually.

Quick verification steps:

1. Run show running-config pre-copy to preview changes.
2. Execute copy running-config startup-config (or copy run start).
3. Confirm with show startup-config—they should match.
4. Test: Reload via reload and check show running-config post-boot.

Common Pitfalls

Forgetting this after configure terminal edits is a rookie trap in CCNA labs—forums buzz with "lost my config!" panic stories from 2025 cert takers. Reverse it with copy startup-config running-config to load old settings live.

TL;DR : Overwrites startup-config in NVRAM with running-config for reboot persistence.

Information gathered from public forums or data available on the internet and portrayed here.