Firewalls are designed to block unauthorized traffic. That’s great for security, but what happens when you do need to let specific connections through, like a remote desktop session or file access? This is where firewall port mapping comes into play.
But here’s the catch: opening ports improperly is one of the fastest ways to let attackers into your system. The same port that lets you access your files remotely could also give cybercriminals a direct route to your network — if not done correctly.
This guide will break down exactly what firewall port mapping is, when you should (and shouldn’t) use it, and how to do it safely without compromising your business or personal data. We’ll also explain the difference between port mapping and port forwarding service, clear up common myths, and help you avoid costly mistakes.
What is Firewall Port Mapping?
Firewall port mapping is the process of telling your firewall to allow specific traffic to reach certain devices or services on your private network. Normally, firewalls block external traffic to keep hackers out. But if you want to connect to a device from outside your network—like a mapped drive or a remote desktop—you need to open (or “map”) specific ports for that purpose.
For example, if you’re working remotely and need access to files on your office computer, you’d map a port that lets you reach that device securely. The firewall will listen for traffic on that port and route it to the right place inside the network.
Port mapping is essential for:
- File sharing between office and remote devices.
- Running home servers, like Minecraft or media servers.
- Remote access to desktops or apps hosted internally.
- Hosting web or FTP servers for external users.
Is Port Forwarding Safe?
Port forwarding is useful for remote access, but it comes with serious security risks. By opening ports to the internet, you expose internal devices to threats like hacking, brute-force attacks, and ransomware. Common ports for services like RDP or SMB are frequently targeted by attackers scanning for vulnerabilities.
To reduce risks, port forwarding should always be combined with IP restrictions, strong passwords, and updated software. However, even with precautions, it increases your attack surface. Using a VPN is a safer alternative, allowing secure remote access without exposing ports to the public internet.
Why You Need Firewall Port Mapping?
Despite the risks, there are many legitimate reasons why businesses and advanced users rely on port mapping. Let’s break down some of the most common cases where mapping ports is essential to keep operations running smoothly:
1. Remote Access to Mapped Drives
If your team needs to access shared files and folders remotely, port mapping makes this possible — especially for small businesses that don’t have enterprise-grade remote file access systems.
For instance, mapping SMB port 445 allows employees to access shared network drives securely if the setup is done correctly. Without this port open, remote access to files simply won’t happen.
2. Hosting Business Services and Applications
Port mapping is critical when hosting services that need to be accessible from outside, such as:
- Internal web applications.
- Remote database connections.
- FTP servers for client file exchanges.
- Voice over IP (VoIP) services.
Without mapped ports, external clients, partners, or employees can’t connect, bringing business processes to a halt.
3. Remote Desktop for IT Management
IT admins frequently need remote desktop access (port 3389) to manage devices without being onsite. Without proper port mapping, remote management isn’t possible, which can be a huge blocker for distributed teams and companies with multiple offices.
4. Hosting Servers (Gaming, Media, IoT Devices)
Home users and businesses hosting gaming servers, media servers, or smart devices often need port mapping so these services are accessible to external users or devices.
What Ports Are Used to Map a Drive?
When you map a drive over a network — especially if you need access from outside — specific ports must be opened to allow traffic through. Below are the essential ports you’ll deal with when mapping drives and related services:
| Service | Port Forwarding Port Number List | Protocol | Purpose |
| SMB (Server Message Block) | 445 | TCP | Main protocol for file and printer sharing |
| NetBIOS Name Service | 137 | UDP | Name resolution within local network |
| NetBIOS Datagram Service | 138 | UDP | Supports file sharing over NetBIOS |
| NetBIOS Session Service | 139 | TCP | File sharing for older Windows systems |
| Remote Desktop Protocol (RDP) | 3389 | TCP/UDP | Accessing desktops remotely |
Why Port 445 is Tricky:
Although port 445 is necessary for mapping network drives, opening it to the public internet is extremely dangerous. Hackers constantly scan for open 445 ports to exploit vulnerabilities. This is why many experts recommend using a VPN or zero-trust solutions instead of direct port mapping — something we’ll touch on later.
Important: You should only map these ports when you know exactly what you’re doing, and only for specific IP addresses when possible to avoid unwanted access.
Port Mapping vs. Port Forwarding – What’s the Difference?
Many people often wonder if port mapping and port forwarding are different. The truth is, port mapping and port forwarding are essentially the same thing in most modern networking contexts. Both terms refer to the process of directing external traffic coming to a specific port on your public IP address to an internal device and port inside your private network.
While some advanced enterprise devices or ISPs might occasionally use “port mapping” to describe specific types of NAT (Network Address Translation) rules, for the vast majority of users and standard routers, port mapping and port forwarding are interchangeable terms.
When you set up port forwarding (or port mapping), you are instructing your router or firewall to allow traffic from the internet to pass through to a designated device, such as a file server, game server, or remote desktop system.
Because port forwarding/mapping opens up a direct line from the public internet to a device on your private network, it significantly increases your exposure to cyber threats. That’s why additional security measures, such as VPNs, strong passwords, IP whitelisting, and firewalls, are critical when using port forwarding.
How to Set Up Firewall Port Mapping (Step-by-Step Guide)
Setting up port mapping (or port forwarding) requires careful configuration on your router or firewall. Below is a step-by-step guide to do this properly and securely:
1. Log in to Your Router Admin Panel
- Open a web browser and enter your router’s IP address (commonly 192.168.1.1 or 192.168.0.1).
- Enter your administrator username and password.
2. Navigate to Port Forwarding or NAT Section
- Look for a tab called Port Forwarding, Applications & Gaming, NAT, or similar.
3. Add a New Port Forwarding Rule
- Service Name: Give it a name like “SMB File Sharing” or “RDP Access”.
- External Port: Enter the port number (e.g., 445 for SMB or 3389 for RDP).
- Internal IP Address: Enter the IP address of the device inside your network (e.g., your office computer).
- Internal Port: Enter the internal port number (often same as external, e.g., 445).
- Protocol: Choose TCP, UDP, or both depending on your use case.
4. Save and Apply the Rule
- Click Save or Apply to finalize the rule.
5. Restrict by IP (Optional but Recommended)
- If possible, restrict access to specific trusted IP addresses to reduce exposure.
Important Tips:
- Avoid using default ports for sensitive services if possible; choose alternative high-range ports for added obscurity.
- Always combine port forwarding with strong passwords and updated software to avoid vulnerabilities.
How to Check if Port Mapping Works (Testing Methods)
Once you’ve set up port mapping, it’s important to ensure that your port is open and accessible.
Here are some of the ways you can check if port mapping is working:
Use Online Port Checker Tools
- Visit sites like canyouseeme.org or portchecker.co.
- Enter the port number you mapped (e.g., 445, 3389).
- Check if the port is open.
Test via Telnet or PowerShell
- On Windows, open Command Prompt or PowerShell.
- Run: telnet [your public IP] [port number] (e.g., telnet 203.0.113.5 445).
- If the connection is successful, the port is open.
Attempt Real Connection
- From an external device, attempt to access the mapped service (e.g., remote desktop, file share).
If port is not open:
- Double-check firewall rules on both the router and device.
- Ensure the service is running on the internal device.
- Confirm the internal IP address hasn’t changed (consider using static IPs).
VPN – A Safer Alternative to Port Mapping?
While port mapping (or forwarding) is commonly used to enable remote access, it comes with inherent risks. Exposing ports to the public internet can make your network vulnerable to hacking, ransomware, and brute force attacks. This is why many businesses and security-conscious users are turning to safer alternatives.
A VPN allows you to securely connect to your internal network over the internet without exposing any ports. VPNs create an encrypted tunnel, protecting data from eavesdropping and unauthorized access.
PureVPN’s White Label VPN solution offers businesses a custom-branded VPN that provides:
- Secure remote access to internal resources without port forwarding software.
- Private encrypted tunnels for employees and partners.
- Controlled access through centralized user management.
- Reduced attack surface by eliminating open public ports.
Conclusion
Firewall port mapping (also called port forwarding) is essential for enabling external access to internal services like mapped drives, remote desktops, or servers. However, poorly secured port forwarding can expose your network to serious risks. Using VPN-based solutions is a far safer approach, especially for businesses.
If you’re a business looking for secure ways to enable remote access without exposing sensitive services to the internet, PureVPN’s White Label VPN offers customizable VPN solutions that allow encrypted remote access — no need to open dangerous ports to the world. Protect your network and enable seamless connectivity today.