Which method confirms port forwarding is accessible from an external network?

• A. Ping the public IP from inside the LAN.
• B. Restart the router.
• C. Check the router's ARP table.
• D. Attempt to connect to the public IP:port from an external network and observe the destination host; check logs and NAT rules for hits.

Answer: (D)

To confirm port forwarding works for external access, you need to test the actual path from an outside network by connecting to the public IP and the mapped port. If a connection succeeds, and you can see that the router treated the traffic as a NAT hit and forwarded it to the internal host (visible in router logs or NAT/firewall counters), you’ve demonstrated that the forward is functioning.

Why this approach matters: port forwarding is a NAT mapping from an external port to an internal IP and port. Testing from inside the LAN by pinging the public IP often won’t prove external reachability due to NAT reflection/hairpin behavior and firewall rules, and simply restarting the router or inspecting local ARP tables doesn’t verify the external path. The direct external test, paired with checking the router’s logs and NAT rule matches, provides clear evidence that the traffic actually traverses the gateway and lands on the intended internal host. If the test fails, investigate firewall settings, correct NAT/forwarding rules, the internal host’s firewall, and any external factors like ISP port blocks.