Troubleshooting Port Forwarding Issues: D-Link DIR-855 NB Router
Are you facing difficulties with port forwarding on your D-Link DIR-855 NB router? This article will guide you through troubleshooting common issues and help resolve them. Whether it's a firewall, NAT, or ISP blocking, we'll cover it all. By the end, you should have a better understanding of what might be causing the problem and how to fix it.
Introduction to D-Link DIR-855 NB Router Configuration
The D-Link DIR-855 NB router is a popular choice for those looking to set up a reliable home or small office network. However, configuring port forwarding can sometimes be challenging. This guide will help you understand why your port forwarding might not be working and how to troubleshoot it.
Common Issues and Troubleshooting Steps
Firewall Misconfiguration
Firewalls can often block incoming connections. Ensure that your router's firewall is not blocking your port forward requests. If your server has a built-in firewall, make sure it is not actively blocking the incoming connections.
Check for NAT Issues
If you're behind NAT (Network Address Translation), your public IP address might not be directly reachable from the Internet. To check if you're behind NAT, visit If you see a public IP address, you are not behind NAT. If you see an internal IP address, you might need to configure your router to access external services.
ISP Restrictions
Your Internet Service Provider (ISP) may block certain server ports, especially those used for email services. If you're trying to open a port for email or web services, contact your ISP to ensure that they are not blocking your port forward requests.
Check Public IP Address
Determine if your public IP address is stable or dynamic. Dynamic public IP addresses can change, which can make port forwarding more complex. If you have a dynamic public IP address, consider using a Dynamic DNS (DDoS) service to maintain consistent access to your server.
Test From Another Network
Try accessing your server from a different network or Internet Service Provider (ISP). Some routers allow you to test port forwards internally, using the Internet address looping back to the same router. However, this method might not always work. If possible, test from a different network to see if the issue is with your router or the ISP.
ShieldsUp Test
Run the ShieldsUp test from Gibson Research Corporation. This will help you determine whether the port is hidden, closed, or open. Visit the ShieldsUp website and enter your public IP address to see the results. If the port is not open, you may have a problem with the router or your firewall configuration.
Testing with a Known Good Router
Try setting up port forwarding with a different router to see if the issue is with your D-Link DIR-855 NB router. A known good router can help you isolate whether the problem is with the router or your configuration.
Bad Configuration
Double-check your IP addresses. Ensure that the server computer is on a static or reserved IP address on the private network. Also, verify that the port forwarding configuration is correct, including the public and private port numbers, and the correct IP address for the server computer.
Summary
Port forwarding on your D-Link DIR-855 NB router can be challenging due to various factors such as firewalls, NAT, ISP blocking, and dynamic IP addresses. By following the troubleshooting steps outlined in this guide, you can identify and resolve the issues, ensuring your server is accessible from the Internet. Always refer to the router's documentation and manufacturer's support forums for additional help if needed.