What is NAT Firewall? – The Lowdown

Getting results from your search engine is a breeze – but behind the scenes, things are a lot more complicated than that. There are all sorts of tools out there that monitor your traffic to make sure your network is secure, but one of the most important ones you may not even know about is a NAT Firewall – or Network Address Translation. You might be surprised to learn that you probably have one on your router already – its the thing that lets your router connect your private network to the internet using NAT, allowing all your devices to talk to the wider world using just one IP address.

First off, let’s talk about what a firewall actually is. Essentially its like a personal assistant for your computer – think of your PC as a director, and the firewall as their trusted secretary, sorting through all the incoming and outgoing mail and only letting in the stuff that the director wants to receive.

When you browse the internet, stream a movie or send an email, you’re sending all sorts of requests to different servers – and the firewall sits between your local network and the wider world, sorting out the incoming and outgoing data to make sure everything matches up. If it doesn’t, it just gets tossed.

And the good news is that the firewall protects you from all that dodgy stuff lurking on the web that could do you harm.

Conspiracy

Jan 15, 2026

9 min read

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Types of Firewalls

There are three main types of firewalls out there:

Software firewalls
Hardware firewalls
Cloud-based firewalls

And each one uses its own methods to keep the bad guys out – which means they’re all a bit different in terms of how reliable they are.

What is Network Address Translation (NAT)?

So, NAT is a bit of a solution to the problem of the IPv4 protocol running out of IP addresses. There just aren’t enough unique IP addresses to go around, and that was a problem they didn’t think would happen when they first came up with IPv4 – they thought 4.3 billion would be enough.

But then people started getting multiple devices connected to the internet, and suddenly we had a shortage. A NAT gateway lets all the devices in your private network share a single public IP address, which helps to conserve those limited IP addresses.

What is NAT Firewall?

A NAT firewall is then a special kind of a firewall that resides in your router and its role is to defend your own network by only permitting traffic to be sent to and also out of this network when it receives a request by a device within your own personal network. It also has a covert name – its internal ip address is not published to the rest of the world.

When routers are connected to the internet, they are given one public IP address and that is the address that all your devices use to communicate with the rest of the world. But every device in your network has got its own internal IP address – and the NAT firewall agrees to map all those internal addresses to only one public address, and then you can all be connected to the internet without all having to be assigned their own unique IP address.

How it works

Here is how a NAT firewall works: when one of your devices makes a request that goes to a web server, the NAT firewall modifies the destination IP address of the data packet – in that manner, the internal devices can communicate with the external servers without ever disclosing their own IP addresses. And since the NAT firewall is controlling the flow of traffic it is also able to block out any suspicious content that may be attempting to sneak in too.

The NAT firewall works by changing the internal IP addresses in the data packets to the router’s public IP address, and also by assigning unique port numbers to each connection – which allows multiple devices to share the same public IP address. And the router keeps a record of all these changes in a special table called the forwarding table.

There are different types of NAT – like dynamic NAT, which maps internal IP addresses to a pool of external addresses, and static NAT, which uses one to one mapping between an internal and an external IP address for consistent access – often used for servers.That information gets routed back to the router. NAT re-routes the data back to the device that initiated the request. What this means is that NAT manages network traffic on the router & keeps internal IP addresses hidden from external networks, thereby enhancing security by blocking unsolicited inbound traffic. If it didn’t, the same data would be received by all devices connected to the router, which isn’t what you’d want.

Now, the public IP address of the data packets gets changed back to the original private IP and data packets are forwarded to the device that needs them. NAT settings on your router along with NAT configuration can impact connectivity, particularly for online gaming and peer to peer connections – where setting things up right is super important for smooth performance. The job of NAT is to handle inbound traffic, keep unsolicited connections at bay and protect internet connected devices.

When multiple devices on the same network are using a single IP address, NAT’s port address translation feature lets that one IP address be shared. And of course NAT helps keep track of IP address information for all devices.

Port Forwarding with NAT

Port forwarding with NAT – that’s the key to letting devices outside your private network connect directly with your internal devices. Usually, NAT acts as a gatekeeper – all your local devices get to share the same public IP, whilst hiding their internal IPs from the outside world. But what if you need someone from the outside world to be able to reach a particular device or service inside your private network. That’s where port forwarding comes in.

When your private network sends data out to the ‘net, the NAT device (which is probably your router) swaps the source IP address of each packet from the private IP to its public IP address. All your devices appear to be coming from that one public IP. The router keeps track of which internal device made each request, so when responses come back, it knows just where to send them.

Port forwarding rules take this a step further. By setting up port forwarding, you tell your NAT device to listen for incoming traffic on a specific port of its public IP address and forward that traffic to a specific port and private IP address inside your network. For example, if you’ve got a web-server running on your home network, you can configure your router to Forward all incoming traffic on port 80 (that’s the standard web-server port) to the private IP address of your web-server. Then, anyone who types in your public IP address into their browser can access your web-server, even though its actually running on a private IP address behind the scenes.

This is especially useful for online gaming, for remote desktop access or any time you need to target specific devices on your internal network from outside. Port forwarding rules let you direct internet traffic to the right device, even though all your devices share the same public IP address.

But with this power comes great responsibility. If you’re not careful and just open up ports without proper security in place, you could be leaving your internal devices open to unwanted attention from the ‘net. You should only forward the ports you need, use strong passwords and keep your devices up to date to minimize security risks. NAT hides your internal network structure from view, but port forwarding can create openings if you don’t keep things properly managed.

Beyond just letting access to internal services, port forwarding with NAT also helps save IP address space. By letting multiple devices share one public IP, NAT reduces the need for unique IP addresses and makes it easier to manage your network. At the same time, it’s good for network security because it keeps internal private IP addresses hidden from external networks.

In a nutshell, port forwarding with NAT is a handy way to let external devices reach specific services on your private network. By setting up port forwarding rules, you can target specific devices while still reaping the benefits of the security and IP address savings NAT gives you. Just remember to take a good hard look at your NAT firewall settings and security measures to make sure your network stays safe and secure.

Does NAT protect your private IP addresses?

The fact is that a NAT is not exactly a safety feature but rather a hardware feature. Instead, it provides a safeguard to the users by concealing their internal IP addresses to the outside world instead giving them one IP to operate with. NAT provides an extra security and ensures that external threats do not have access to internal IP addresses so that hackers have difficulty in attacking devices in your network.

The thing it also does is to make sure a certain device is required to seek permission prior to accepting any traffic. And in case any malicious packet is received which is not contained in the list of expected communications, it is rejected. Certain firewalls even prevent outgoing traffic that one does not want by white listing. Even though it may appear like a great idea, even when you accidentally press a malware link, it will not be able to get in touch with your device.

There are higher order attacks though, and they may well breach NAT. Those may social engineer or phish to your device. However, with help of NAT, your IP address does not make an easy prey among hackers. With a network firewall and your NAT, you get an all round protection against a entire gamut of threats.

NAT and VPN: allowing multiple devices

There’s a common myth that you shouldn’t use a VPN with a NAT. Is that true?A VPN is supposed to encrypt your internet traffic before it ever hits the internet – basically creating a secure tunnel for all online activity via a secure VPN connection by routing your traffic through those encrypted tunnels.

If you want your router to function properly, it needs to know something about whats going on with that traffic. The trouble is, older VPN protocols don’t let the router get the information it needs. As a result, they can just be blocked out. To avoid this problem, make sure your router has a VPN pass through. Many VPN providers are also adding NAT firewalls & port-blocking as a way to further boost user privacy and security.

Luckily, a lot of them have figured out how to get their traffic through – but if yours hasn’t, some of the worlds most popular VPNs are now offering improved protocols that should be able to handle this sort of issue.