What is NAT and how does it work?

Nadin Bhatt
Nadin Bhatt | Writer
Last updated: April 8, 2021
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With more than 350 million internet users and in excess of 100 million hosts, it’s safe to say that the internet has grown exponentially ever since its inception. This certainly doesn’t show any signs of changing any time soon with these figures due to increase massively as the years go by.

In an effort to combat these growing numbers, NAT – also referred to as Network Address Translation – is used to allow multiple client requests over a single private IP address. That’s all well and good, but what exactly is NAT and what does it mean for internet users? Luckily, you’ll find out more about what NAT is all about in the following guide.

We will also cover what a NAT Firewall is – including how it can protect multiple devices while making the use of IP addresses much more efficiently than was previously the case. You will also discover how a NAT firewall is particularly relevant to Virtual Private Network (VPN) users.

If you were hoping to discover more about NAT and NAT firewall and exactly how they work, continue reading as our complete guide will cover all of the essential information when it comes to the aforementioned terms.

What is NAT?

NAT refers to Network Address Translation, which was developed to make IP addresses more efficient. This ensures that unregistered IP addresses can correctly connect to the internet, which is common among private IP networks. This effectively governs the distribution of packets over a network.

Originally developed to conserve the public internet address space, NAT has ensured that the ever-increasing number of computers connected to the internet can be accommodated in a world where internet providers have witnessed exhaustion of the available supply of IP addresses. This had the potential to heavily limit the growth of the internet, something that would be a disaster in the current day where the number of internet-connected devices is constantly on the rise.

When it is set up to run on a router, NAT allows for two networks to be connected together. Private addresses within the internal network are then translated into legal addresses, prior to the forwarding of packets to another network. Offering extra security by concealing the entire internal network behind the given address, NAT can be configured to show the outside world just one address for the entire network.

NAT enables computers on a local network to share one common outbound connection. It simultaneously achieves IP address conservation and enhanced security with the effective mapping of the private IP addresses of all devices to a single IP address seen by external users. This is usually applied to remote-access environments.

How does NAT work?

Acting as an agent between a public network and a local network, NAT can be set up on a single device such as a router which means that only a single unique IP address is needed to cover an entire group of computers. This allows for enhanced security as only one IP address will be seen by any outsiders.

Adjusting the source or destination address accordingly, NAT reproduces the configured address mapping in the IP protocol head and the corresponding checksums. NAT essentially reviews the content of incoming and outgoing IP messages to achieve exactly that.

In the event an external computer attempts to access a computer within a local network, the user will only be able to see the address of the router, with Network Address Translation able to support both dynamic and fixed mappings of one or more internal and external IP addresses.

In turn, this adds an additional layer of security which is perfect for those who have multiple devices on the same network which each contains sensitive data. This is especially relevant as firewalls can be set up on devices such as routers – which only allows authorized systems to access computers in a local network.

So, now that we’ve provided you with the essential knowledge of NAT, it’s time to delve deeper into a NAT firewall – covering exactly what it does and its relevance to anyone who uses a Virtual Private Network (VPN).

What is a NAT Firewall and how does it work?

NAT Firewalls are used as an additional layer of security that blocks unrequested inbound traffic when you are connected to a particular network. It is a method of protection that is often utilized by VPNs and ensures that when you are connected to a server on the VPN service, any device you are running through the VPN will be protected.

Usually, a NAT router helps to filter out a lot of malicious traffic and undesirable IP addresses. But, when a NAT firewall is used, a VPN service can cause interference, which leaves your devices vulnerable to attack. Tunnels created by VPNs effectively bore straight through NAT protections, and so you will have to take appropriate measures to prevent this from ever happening.

A NAT firewall that is used by a VPN allows you to benefit from the protection that is offered by a standard NAT router, while also allowing you to enjoy the enhanced privacy that VPNs are able to offer. When used in combination, a NAT router and a VPN NAT firewall work hand in hand, which means the following:

  • The likelihood of hackers finding open ports or injecting malware into your data transmissions is heavily reduced as they will find it more difficult.
  • You will know where each packet of data is coming from and whether you are sending the correct data as each packet sent over your VPN will be inspected and verified.
  • NAT firewalls help to maintain the integrity of the privacy services offered by the VPN while providing some protection against encryption attacks.

Ensuring NAT firewall protection with a VPN

While it isn’t totally necessary to combine a VPN and NAT firewall, it’s well worth considering if you would like to obtain the benefits of each method of online privacy protection. Getting a NAT router up and running certainly won’t come cheap. But, if it’s within your budget it might well be worth considering – particularly if you need to protect numerous devices on one network.

With that in mind, the following section will provide some of our recommended VPNs which ensure NAT firewall protection.

  1. IPVanish

While they don’t include local NAT firewalls, IPVanish understands the need to have effective NAT safeguards. Known for their focus on privacy and speed, they make use of a firewall between their servers and ISPs. In turn, this allows users to share the same IP address. This is similar to ExpressVPN’s system, although it comes complete with extra NAT protection.

  1. CyberGhost

NAT protection comes standard with CyberGhost as part of their package, with the added benefits of 256-bit AES encryption, IPv6 leak protection and IP sharing – so pretty much every security concern is covered here. This makes it the perfect choice for those who torrent regularly.

  1. NordVPN

Every user of NordVPN gets their own IP address – making NAT filtering absolutely essential for optimal online security. As one of the most respected VPN providers around, you can also benefit from plenty of other security countermeasures. As the company explains, NAT filtering effectively screens material that you didn’t “request.” However, NordVPN made the decision to include anti-virus and malware protection too, as NAT doesn’t cover this automatically.

  1. PureVPN

PureVPN is a service which refers to the NAT issue as “port forwarding.” This is essentially the same thing as NAT firewall protection. This particular VPN, which is widely used around the world, includes the option to switch on port forwarding for as many as 5 devices. However, if you’re a PureVPN fan, just remember that this isn’t switched on by default.

  1. Ivacy

Offering NAT as a paid-for extra, Ivacy’s plans are highly affordable – usually just an additional $1 per month per subscription. Their NAT service is also tailored to business users in a way that many other VPNs aren’t, as it offers port forwarding, readdressing, port multiplexing, and multiple device protection.

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  1. 5678Brooklynwilson

    I understand the role NAT plays in securing IP addresses. However, the reliability of this security is threatened by the leakage of some internal services to the outside world

  2. Aaron

    According to the article, you said NAT enables computers on a local network to share one common outbound connection. So my question is can NAT be used by home users to allow multiple computers to connect to a broadband connection?

  3. Peter Timerman

    NAT was a very clever idea for fixing the shortage of IP Addresses, and it’s stills very useful today. Its history is actually very interesting, I’ll keep in reading about it.

  4. ZakCooke

    I am sure that many people do not know that with NAT they can make multiple client requests over a single private IP address. It also enable private IP networks that use unregistered IP addresses to correctly connect to the Internet.

  5. rhinoo2002

    Well, from what I know, NAT is a very poor protection mechanism. It can be circumvented in many ways and it is known to have caused headaches to network administrators.

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