What is a NAT firewall and how does it work?

What is a NAT firewall and how does it work?

Written by Ramsay, In Technology, Published On
June 22, 2023
Last modified on June 26th, 2023

NAT stands for Network Address Translation, a computer networking technology that enables many devices to share a single gateway to the internet. This gateway has the same public IP address and a unique personal IP address. A firewall is a shield that prevents unwanted communications between devices. A NAT firewall only allows internet traffic if a device requests it.

The router sorts data to ensure a suitable device gets the web content. The NAT firewall is a network security layer that limits malicious traffic, such as hackers.

Different types of firewalls – Method of operation


When it comes to firewalls types, there are five more key sub-types:

  • Packet-Filtering Firewalls
  • Circuit-Level Gateways
  • Stateful Inspection Firewall
  • Proxy Firewalls
  • Next-Generation Firewall

Small companies use packet-filtering firewalls, which protect the network layer. Circuit-level firewalls protect the session layer of the network; they have high security.

Stateful inspection firewalls operate on the network and transport layers, providing excellent protection. Proxy firewalls work between internal and external traffic on the application layer. Next-generation firewalls act on all layers except the physical layer and have all the security features.

Definition of NAT

Basic NAT is a one-to-one translation of IP addresses that enables connections across addressing incompatible networks. By changing the IP header information in packets while they are in transit, network address translation (NAT) maps the IP address space. NAT, which set out to avoid giving hosts new addresses, is now crucial for preserving the global address space in the face of IPv4 address exhaustion.

Definition of NAT firewall

A router function adds a layer between devices and the internet called a NAT firewall. It filters traffic and provides safe online security. NAT translates the information, which stands for Network Address Translation.

Computers may communicate via data packets, making locating the information they want possible. A network security tool is a firewall that filters and analyzes incoming and outgoing network data. Security and addressing the lack of IPv4 are its two primary purposes.

How does a NAT firewall work?

A NAT firewall sends a website’s name to a router, which examines the request and sends it to the web server with the website’s external IP address. After comparing the material received to the internal IP address, the router discards any extra information.

It forwards the website copy to the user’s device using the internal IP address. This method is comparable to an office clerk who only transmits calls from specified clients to the user, ensuring that only those calls are for the user if they are that customer.

How does it protect you?

A firewall checks the validity of data packets by examining their source and excluding those that appear suspicious. Hackers find it more challenging to insert malware, find open ports, and carry out cryptographic attacks using NAT firewalls.

They provide extra protection by comparing search results by prohibiting unauthorized internet traffic from entering your private network.

Do VPNs use NAT firewalls?

Due to encryption, the NAT firewall on your router cannot filter out data packets in VPN communication. Your device’s VPN server and client can only decrypt the data. Due to this, the router becomes blind while handling VPN traffic, sending it along without determining if the packets are malicious.

Due to VPN, passthrough permits connections to travel through the router without being examined, so certain routers don’t interfere with VPN traffic. At the server level, VPN providers use NAT firewalls.

The VPN server decrypts requests and sends them to the proper web server. The communication returns to your device, where the VPN client interprets it. The server removes any extraneous packets and re-encrypts them.

Difference between PAT and NAT

Regarding a PAT firewall, PAT, or Port Address Translation, is commonly used with NAT. PAT does similar tasks to NAT but uses ports to connect to the internet and monitor devices on a local network.

For instance, a computer’s internal IP is enabled through its port number rather than being immediately transformed into an external one. As a result, local network devices can be tracked and secured better.


Routers must have NAT firewalls to protect their networks against harmful traffic. VPNs, however, are unable to identify and stop malicious traffic. Always use a VPN that has its own NAT firewall on its servers to assure security. Additionally, VPNs must feature kill switches, no-log rules, leak prevention, and encryption. Please include any extra security measures you have in the comments or on social media.

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