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What is Network Address Translation (NAT)? Static, Dynamic and Hide NAT Explained

Why NAT Matters

In today's digital world, it's normal to have dozens of devices connected to the internet in a single home — smartphones, laptops, tablets, smart TVs and even smart appliances.

But here’s the catch: your internet service provider (ISP) likely gives your router just one public IP address. So, how do all your devices get online at the same time?

This is where NAT (Network Address Translation) steps in — a critical technology that allows multiple devices on a private network to share a single public IP address when accessing the internet and more.

We already briefly introduced NAT with a practical example in How Private IPs and Public IPs Work Together? as part of our article What is an IP Address?. In this article, we’ll go deeper — exploring how NAT actually works, its different types, real-life usage examples, and its impact on security and connectivity.

Here’s a simple way to understand it:

Imagine your network is a call center. Inside, each employee (device) has their own extension number (private IP). But the call center only has one phone number (public IP) visible to the outside world. Every time an employee makes a call (sends a request), the administrator (your router with NAT) notes who made it and forwards the call using the main number. When someone calls back, the administrator knows exactly which extension to route the call to.

That’s what NAT does — it keeps track of outgoing requests and ensures incoming responses reach the right device inside your network.

But NAT is more than just a workaround — it’s one of the most important technologies we rarely think about. It:

In the next sections, we’ll explore why NAT was invented, break down the different types of NAT (Static, Dynamic, and NAPT), and walk through practical examples that show how NAT affects everything from your Zoom calls to your online gaming — and even your digital safety.

Why NAT Was Invented

The IPv4 Address Shortage

When the internet was first designed, no one anticipated a future where nearly every home appliance, car, or wearable device would connect online. The IPv4 protocol — the backbone of internet addressing for decades — supports about 4.3 billion total IP addresses. But in practice, only around 3.7 billion of these are usable due to reserved and non-routable blocks. We covered this in detail in Why Not All IPv4 Addresses Are Usable in our article Evolution of IP Addressing.

That might sound like a lot — until you realize how many devices are competing for them.

According to IoT Analytics, the number of devices expected to be connected to the internet — also known as IoT devices (Internet of Things: things like cars, smart appliances, mobile phones, wearables, and more) — is projected to reach 40 billion by 2030. And that number continues to grow rapidly.

The Role of NAT

Faced with a limited number of usable public IP addresses and a rapidly growing number of devices, engineers needed a way to connect more systems without changing the core structure of the internet. That’s when Network Address Translation (NAT) stepped in as a powerful workaround.

NAT allows multiple devices on a private network to access the internet using a single public IP address. It works by translating the private IP addresses used inside a network into a public IP address for outgoing traffic — and then doing the reverse when responses come back.

This translation happens on the router or gateway and is completely invisible to users. It’s what enables your phone, laptop, smart TV, and home assistant to all browse the internet through the same IP, without any interference.

Even more importantly, private IP addresses are not routable over the public internet. That means they can’t reach websites or services on their own — they need to go through a NAT-enabled device that holds a valid public IP address. In short, without NAT, devices on private networks would be isolated from the global internet.

Thanks to NAT, we’ve been able to:

As the next sections will show, NAT comes in different types, each suited to different network setups and goals. But no matter the form, its purpose remains the same: make efficient use of limited IP resources while keeping networks connected and protected.

Types of NAT and How They Work

NAT isn’t one-size-fits-all. In fact, there are multiple types of NAT, each designed for a specific purpose — whether it’s enabling internal devices to browse the internet, making a private server accessible from outside, or securely managing many devices through a single IP.

Let’s break down the three most common types of NAT, how each one works, and where you might encounter them in real life.

1. Hide NAT / PAT / NAPT (Many-to-One)

Also known as:

How it works

Hide NAT is the most widely used form of NAT, especially in home routers and small networks. It allows many devices to share a single public IP address by using different port numbers to track each individual connection.

Here’s what happens behind the scenes:

This way, a single public IP (e.g., 142.250.190.78) can handle hundreds of connections at once — each uniquely identified by a source port.

We covered how ports work in the Understanding Ports section of our Core Internet Protocols article. If you’re unfamiliar with ports, we highly recommend reading that section before continuing.

Real-life usage

This is the NAT method you’re almost certainly using right now if you're connected via home Wi-Fi. It enables your laptop, phone, TV, and smart speaker to all browse the internet and stream content simultaneously — all using just one public IP.

It’s also used in:

Practical example

Imagine you and your roommate are both streaming Netflix at the same time. In this example, Netflix uses HTTPS over port 443 and the server IP address is 192.173.87.34:

  1. Your laptop (private IP 192.168.1.10) sends a request using randomly allocated source port 50200.
  2. Your roommate’s tablet (private IP 192.168.1.20) sends a request using randomly allocated source port 50201.

From the devices’ perspective, the outgoing connections look like:

The router — which is also performing NAT — replaces the source IP with the shared public IP 142.250.190.78 but keeps the source ports unchanged:

  1. The router keeps track of each port-to-device mapping internally:
  1. When the Netflix server replies, the router uses the destination port number to identify the correct device.
  2. The replies from the server 192.173.87.34 look like:
  1. Since the router has stored the port mappings, it knows exactly where to forward each packet:

Bonus Insight: No NAT = No Internet (by design)

Here’s something important: without Hide NAT (or any NAT at all), your private network cannot reach the internet.

That’s because private IP addresses are not routable over the public internet by any router. If your router or NAT device doesn’t translate them into a public IP using NAT, devices on your network will have no way to communicate beyond the local environment.

And in some cases — that’s exactly the goal.

In highly sensitive environments like:

it’s common practice to intentionally avoid using NAT or exposing a public IP at all. These networks are kept completely offline or connected only through isolated, internal systems to prevent any chance of external intrusion.

So while Hide NAT is what connects most of us to the internet seamlessly, its absence is a security feature in environments where zero exposure is a priority.

2. Dynamic NAT (Many-to-Many Mapping)

How it works

Before Hide NAT (also known as PAT or NAPT) became the default approach, Dynamic NAT was introduced to help organizations stretch their limited pool of public IP addresses. It works by dynamically assigning a public IP to a private IP from a pre-defined pool, but without using port numbers for session differentiation.

Here’s the core idea:

This approach allowed devices to connect externally without needing a permanent public IP — at a time when port-level translation (as used in Hide NAT) wasn't yet available or widely adopted.

Real-life usage (when it made sense)

Dynamic NAT was primarily used before Hide NAT existed or became reliable, in enterprise environments where:

This method provided more flexibility than manually assigning static mappings, but it still couldn’t scale to support large numbers of users due to the limited number of public IPs.

Practical example

Imagine a university campus in the early 2000s with 200 computers and only 30 public IPs from their ISP:

This worked — but only if the number of simultaneous connections stayed under the IP limit.

Why it’s rarely used today

With the introduction of Hide NAT (PAT) — which uses port numbers to allow thousands of devices to share a single public IP — Dynamic NAT became largely obsolete. It simply doesn’t scale well.

In modern networking, PAT has replaced Dynamic NAT almost entirely — offering better performance, more flexibility, and minimal reliance on scarce public IPs.

Today, if you're using a router at home, in a coffee shop, or even in most offices, you're using Hide NAT, not Dynamic NAT.

3. Static NAT (One-to-One Mapping)

How it works

Static NAT creates a permanent, one-to-one mapping between a private IP address and a public IP address. Unlike Dynamic NAT, which assigns public IPs temporarily, Static NAT ensures that every time a specific private IP sends traffic, it will always use the same public IP — and vice versa.

This also means that external devices can initiate connections to that internal device through its assigned public IP, which makes Static NAT ideal for services that need to be accessible from the internet.

Real-life usage

Static NAT is typically used when:

You’ll often find Static NAT in:

Practical example

Let’s say you run a home server on 192.168.1.100 and want people to access your website from the internet. Your ISP gives you a public IP address: 142.250.190.78.

Using Static NAT, you configure your router so that:

Now, no matter where someone is in the world, if they type 142.250.190.78 in their browser, they’ll reach your internal server.

Tradeoffs

While Static NAT provides predictable external access, it comes with tradeoffs:

That’s why Static NAT is typically used only for specific needs and not for general internet access across a network.

What About IPv6?

Until now, we’ve talked about NAT in the context of IPv4, which is where it was born and where it’s still heavily used. But what happens when we shift to IPv6, the newer version of the Internet Protocol?

NAT Isn’t Required in IPv6

IPv6 was designed with one major goal in mind: solving the IP address shortage.

Instead of offering 4.3 billion addresses like IPv4, IPv6 supports 340 undecillion addresses — that’s 340 followed by 36 zeros. In practice, this means every single device on the planet can have its own unique, public IP address.

Because of that:

But NAT Still Exists (Sort of)

That said, some network engineers and organizations still implement NAT66 (NAT for IPv6), often for:

However, these use cases are rare and usually discouraged. The creators of IPv6 designed it to work without NAT, relying instead on firewalls, access control lists, and modern security tools to protect devices.

So what about security?

Many people mistakenly believe that NAT provides real security. In truth, the protection you're used to in NAT-enabled IPv4 networks comes from devices called stateful firewalls, not NAT itself.

We’ll cover firewalls and best practices in detail in our upcoming article “Cybersecurity and Privacy Fundamentals.”

In IPv6, you still need firewalls and good security practices — NAT is just no longer used as a barrier by default.

IPv6 Is the Future — But We're Still in Transition

Despite its advantages, IPv6 adoption is still incomplete. As of 2025, many ISPs, data centers, websites, and users still rely on IPv4.

That’s why NAT continues to play a critical role in today’s internet. But over time, as IPv6 becomes the norm, we may finally say goodbye to NAT as a technical necessity.

Final Thoughts

Network Address Translation (NAT) was never meant to be a long-term fix — yet it became one of the most important tools that kept the internet running through decades of growth.

By allowing entire private networks to share a single public IP, NAT helped conserve IPv4 addresses, simplified connectivity for homes and businesses, and even added a basic layer of network separation.

While NAT has its limitations, especially when it comes to scaling, real-time communications, or hosting services, it’s still a cornerstone of modern networking. And until IPv6 becomes truly universal, NAT will remain relevant for most users and systems.

Understanding how NAT works — and how each type fits into different network environments — gives you a clearer picture of what’s happening behind the scenes every time you open a browser, join a Zoom call, or stream a show.

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