Why a copied running configuration might not work You copied a configuration from a network host into the router's RAM (running-config). The configuration looks correct, but nothing works. What is the most likely cause in this scenario?

Introduction / Context:
On Cisco devices, interface state is an explicit configuration element. If an interface is administratively shut down, it will remain down until a no shutdown command is applied, even if you paste or merge a configuration that contains IP addressing and other settings. Understanding merge semantics explains why a seemingly correct running-config may not pass traffic after being copied in.

Given Data / Assumptions:

• You copied a valid-looking configuration into running-config (RAM).
• Interfaces still show administratively down (or line protocol down).
• No device reload occurred; the configuration was merged, not replaced.

Concept / Approach:

Copying or pasting configuration lines merges with the existing running-config; it does not automatically negate pre-existing commands. If an interface previously had the shutdown directive, and your pasted configuration did not include no shutdown, the interface will remain disabled. This is a common oversight when restoring configurations on lab or field devices.

Step-by-Step Solution:

Verification / Alternative check:

Use show running-config to ensure no shutdown is present. Confirm L1/L2 status with show interfaces and end-to-end pings or routing adjacencies forming (for example, show ip ospf neighbor).

Why Other Options Are Wrong:

• Wrong config (A) is possible but not the most likely reason when the pasted lines look correct.
• Copying into flash (B) would not alter running-config at all; the prompt states you copied into RAM.
• IOS corruption (D) or ROMMON fallback (E) would present different symptoms (reboots, missing commands, or ROMMON prompt).

Common Pitfalls:

• Assuming copy replaces instead of merges; always include necessary no statements (like no shutdown).
• Forgetting to save changes to startup-config using write memory or copy run start.

Final Answer:

The copy did not override the shutdown command in running-config.