What Is a NAT Firewall? Complete 2024 Guide

Paige Henley
Published on: September 20, 2024 Editor

A Network Address Translation (NAT) firewall acts as a security gatekeeper for your home or small business network. It helps keep your devices safe by masking their IP addresses and blocking unwanted connections. With a NAT firewall, your network is more secure because it only allows in the data you request, making it tougher for hackers and unwanted traffic to access your network.

However, this type of firewall is just one piece of the overall security puzzle. To keep your network fully protected, you’ll also need other security tools like a VPN, which encrypts your data and hides your online activity (I recommend ExpressVPN). You’ll also need antivirus software, which scans for and removes malware. These tools work together to provide comprehensive protection against various cyber threats.

In this guide, you’ll learn everything you need to know about NAT firewalls — how they work, their benefits and limitations, and who should use them. I’ll also dive into how NAT firewalls fit into a broader network security strategy, helping you keep your digital life safe and secure. Editors' Note: ExpressVPN and this site are in the same ownership group.

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How Does a NAT Firewall Work?

A NAT firewall is essentially a “gatekeeper” for your home network. When you have multiple devices like laptops, smartphones, smart TVs, and gaming consoles all connected to the same Wi-Fi network, they share one public IP address that your internet service provider (ISP) assigns to you. This public IP is like your network’s street address that the rest of the internet sees.

Each device inside your network has its own private IP address. Think of it as the apartment number in a big building — it’s unique within your home, but not visible to the outside world. For example, your laptop might have an IP like 192.168.XXX.X, while your smartphone might have 192.168.XX.X.

These are called 32-bit IPv4 private IP addresses, which follow a specific format (like 192.168.X.X). They help your router distinguish between different devices within your network. Each device gets its own private IP address, allowing the router to manage internet traffic and send information to the correct device.

Here’s where the NAT firewall comes into play. When one of your devices (such as your laptop) wants to access a website, it sends a request through the router. The router uses Network Address Translation (NAT) to swap out your laptop’s private IP with your network’s public IP. The website sees the public IP and sends back the information you requested. When that data returns to your router, the NAT firewall figures out which device originally asked for it — your laptop, in this case — and sends the information back there.

This process happens for every device in your network. Whether it’s streaming a show on your TV, checking your email on your phone, or playing an online game on your console, the NAT firewall ensures each device gets the data it needs while sharing that single public IP.

The Role of NAT in Network Security

A NAT firewall leverages the NAT process to provide an additional layer of security. When a device on a local network sends a request to the internet, the NAT firewall modifies the packet’s source IP address from its private address to the public IP address of the NAT device (usually a router).

When the response is returned, the NAT firewall translates the destination IP address from the public IP to the appropriate private IP, directing the packet to the correct device on the local network. This process provides several key security benefits:

• Hides internal IP addresses: By translating private IP addresses to a single public IP, a NAT firewall effectively masks the internal network structure from external entities, making it harder for attackers to identify and target individual devices.
• Blocks unsolicited traffic: A NAT firewall only allows inbound traffic that is part of an ongoing conversation initiated by a device within the network. Unsolicited incoming traffic is dropped, preventing unauthorized access.

Different Types of NAT: Stateful vs. Stateless

NAT firewalls can be categorized into 2 main types based on how they handle connections — stateful and stateless.

• Stateful: This type of firewall is like a vigilant gatekeeper who remembers everyone who comes in and out of a building. It keeps a list (or “table”) of all active visitors (connections) and only allows people back in if they were initially invited (requests from within the network). This means if someone inside the building asks for a delivery, the gatekeeper will recognize the delivery person and let them in. This approach offers higher security because the gatekeeper is always aware of who should be coming in based on the ongoing interactions.
• Stateless: On the other hand, a stateless NAT firewall is more like a gate that follows a fixed set of rules without any memory of previous entries or exits, as it doesn’t track active sessions like a stateful NAT. It doesn’t keep track of who is inside or outside; it simply allows or denies entry based on a basic rulebook (a static rule set). While this approach is straightforward, faster, and easier to manage, it’s less secure because it doesn’t adapt to the current situation — like a gate that might accidentally let in someone pretending to be a delivery person, just because the rulebook says deliveries are allowed.

NAT Firewall vs. Traditional Firewall

NAT firewalls and traditional firewalls serve different purposes. Here are the primary differences:

• NAT firewall: Primarily focuses on translating IP addresses and blocking unsolicited inbound traffic, making it a passive security measure that works well in combination with other security tools like a virtual private network (VPN). NAT is built into most home Wi-Fi routers.
• Traditional firewall: Monitors and controls incoming and outgoing network traffic based on predetermined security rules. It can be more granular in controlling which types of traffic are allowed or blocked.

Use a NAT Firewall and a Good VPN for Ultimate Protection

When combined with a reliable VPN, a NAT firewall can greatly enhance your online security. A VPN encrypts all data traveling between your device and the VPN server, making it unreadable to anyone who might try to intercept it. Meanwhile, the NAT firewall adds an extra layer of protection by blocking any unsolicited incoming traffic at the VPN server level.

This powerful combination works together to keep your data private and secure. The VPN’s encryption ensures that your information stays hidden from prying eyes, while the NAT firewall ensures only safe, legitimate traffic reaches your device. Some VPNs even come with NAT firewalls built-in, like NordVPN.

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Benefits and Limitations of Using a NAT Firewall

NAT firewalls come with pros and cons. I’ll break down the upsides and potential downsides in a way that’s easy to understand.

Benefits of Using a NAT Firewall

A NAT firewall brings several benefits to the table, especially when it comes to protecting your devices and data. Here’s how it works in your favor:

• Keeps your internal IP addresses private: A NAT firewall hides your devices’ private IP addresses from the outside world. Imagine it like a screen that blocks outsiders from seeing into your home. All they see is the main front door (your public IP address), but not the individual rooms (your private IP addresses). This makes it harder for hackers to identify and target specific devices, like your laptop or smartphone.
• Blocks unwanted traffic: A NAT firewall acts like a bouncer at a club. It only lets in responses to requests that were initiated from within your network. If a device on your network, like your laptop, asks for information from a website, the NAT firewall will allow that data to come back in. But if someone out of the blue tries to send data to your network, it’ll be blocked. This helps prevent cyber-attacks and keeps unwanted traffic at bay.
• Works well with VPNs: When you use a VPN with a NAT firewall, you get a double layer of security. The VPN encrypts your data, so no one can read it, while the NAT firewall blocks unsolicited traffic from ever reaching your network. It’s like having both a lock on your front door (NAT firewall) and tinted windows (VPN) for added privacy.
• Simple and automatic protection: NAT firewalls work automatically without much setup or configuration needed from you. They’re often built into routers, which means you don’t have to worry about buying extra hardware or software. It’s like having a built-in safety feature in your car — just set it and forget it!

Limitations of Using a NAT Firewall

While NAT firewalls are great at what they do, they’re not perfect. Here are some things to keep in mind:

• Can’t inspect what’s inside the traffic: A NAT firewall only looks at the outside label on the “package” (the IP address), not what’s inside. This means it can’t detect or block malicious content like viruses, phishing attacks, or malware hidden in the data. Think of it like a security guard who checks the delivery address but doesn’t open the box to see if there’s anything dangerous inside. This is why having a good antivirus program (like Norton) or additional security software is still important.
• Potential compatibility issues: Some applications and services need direct communication between devices, which can be tricky behind a NAT firewall. For example, Voice over IP (VoIP) calls, online gaming, or remote desktop tools might not work smoothly because they often require incoming connections that the NAT firewall blocks. If you’ve ever had trouble getting your online game to connect or your video call to go through, a NAT firewall could be the culprit.
• Doesn’t replace a traditional firewall: While NAT firewalls offer good basic protection, they’re not a substitute for traditional firewalls, which offer more advanced controls over what types of traffic can enter or leave your network. Think of a traditional firewall as a strict security team that checks ID cards and asks questions, while a NAT firewall is more like a simple gate that just checks if you’ve got the right address.

Who Should Use a NAT Firewall?

A NAT firewall is a solid, low-maintenance option for anyone looking to add an extra layer of security to their network without much hassle, and it’s built into most WiFi routers. It’s especially useful for people who want to protect multiple devices in their home or small office without diving into complex security configurations.

Here’s a closer look at who would benefit most from using a NAT firewall:

• Home users looking for basic security: A NAT firewall can help protect all your Internet of Things (IoT) devices by blocking unwanted traffic. It’s a great way to keep things simple while ensuring a basic level of protection for your family’s online activities.
• Small business owners: Small businesses with limited IT resources can also benefit from a NAT firewall. It provides an easy-to-manage solution that helps protect against unsolicited traffic and potential cyber threats without the need for a dedicated IT team to monitor and configure advanced firewall settings.
• People who use VPNs: If you’re already using a good VPN like ExpressVPN to encrypt your data and protect your privacy, adding a NAT firewall gives you an extra layer of defense. While the VPN encrypts your data, the NAT firewall stops unwanted traffic from reaching your network. This combination can be especially beneficial for remote workers, digital nomads, and anyone concerned about online privacy and security.
• Users with simple network needs: If your network mainly consists of web browsing, streaming, and basic online activities, a NAT firewall can provide automatic protection without the need for additional configuration or specialized knowledge.

Enabling NAT (Network Address Translation) on your Wi-Fi router is a key step in securing your home or small business network. NAT is usually enabled by default on most routers when they operate in Router Mode, but if you need to check or manually enable it, the process may vary depending on the router brand and model.

Editors' Note: ExpressVPN and this site are in the same ownership group.

How to Check that NAT is Enabled on Most Routers

1. Access your router’s admin panel: Open a web browser and enter your router’s IP address (commonly 192.168.1.1, 192.168.2.1, 192.168.0.1, and sometimes 192.168.68.1 in the case of TP-Link routers) in the address bar. Some routers also come with an app you can download, such as TP-Link’s Deco app. Either way, log in using your admin credentials. If you haven’t changed them, they might be set to defaults like “admin/admin.”
2. Navigate to the advanced settings page: Look for a section labeled Advanced, Network, or LAN Settings. The exact location can vary, but it’s generally under a broader “Network” category.
3. Check the NAT setting: Once in the advanced network settings, look for NAT, NAT Forwarding, or Routing options. In most cases, NAT will be enabled by default, especially if the router is set to “Router Mode”.
4. Enable NAT: If you find an option for NAT and it’s set to Disabled, switch it to Enabled. Some routers may offer different types of NAT settings, such as Open, Moderate, or Strict. For general use, Moderate or Strict settings are more secure but may affect certain applications like gaming or remote desktop tools.
5. Save changes and reboot: After enabling NAT or adjusting its settings, click Save or Apply. Reboot your router to ensure the changes take effect.

Frequently Asked Questions

What does NAT stand for?

NAT stands for Network Address Translation, a process that modifies the IP addresses of data packets as they pass through a router or gateway. It allows multiple devices on a local network to share a single public IP address when connecting to the internet.

By translating private IP addresses to a public IP, NAT keeps individual devices hidden from the outside world, enhancing network security. It also conserves the number of public IP addresses needed, which is crucial given the limited availability of IPv4 addresses.

What is the purpose of a NAT firewall?

A NAT firewall’s primary purpose is to protect your network by hiding your devices’ private IP addresses and blocking unsolicited inbound traffic. It acts as a gatekeeper, only allowing in data from sources you’ve requested, making it harder for hackers to target specific devices.

This layer of security is especially beneficial for home or small business networks where multiple devices share a single public IP address. By using a NAT firewall, you reduce the risk of unauthorized access and keep your online activity more secure without requiring complex configurations.

Should I enable or disable NAT?

You should generally enable NAT on your router or network to add an extra layer of security by hiding your devices’ private IP addresses. NAT helps manage incoming and outgoing traffic, making your network more secure from potential cyber threats. Generally speaking, Wi-Fi routers will enable NAT by default — as long as you’re using Wi-Fi Router Mode instead of Access Point Mode.

However, in some cases, like certain gaming or remote access applications that require direct inbound connections, NAT can cause connectivity issues. In such scenarios, you might need to configure port forwarding or disable NAT temporarily to allow these connections to work correctly.

Is a NAT not a firewall?

Technically, NAT (Network Address Translation) is not a traditional firewall. However, NAT can act like a basic firewall by blocking unsolicited inbound traffic and hiding your internal IP addresses. This makes it an effective security tool, especially when combined with other measures like a VPN.

While NAT provides some protection, it does not inspect or control traffic content like a traditional firewall does. A full-featured firewall offers more advanced security features and is better for environments needing tighter controls over network traffic.