Mar 28, 2024

Firewalls 101: Network Address Translation (NAT)

Paul Painter, Director, Solutions Engineering

As a solutions engineer guiding clients through diverse technologies, I believe the firewall remains a commonly misconstrued element. Its basic functions and the added benefits of advanced features often elude understanding. That’s why we are embarking on a comprehensive series where we delve into the intricate world of firewalls, discussing their fundamental concepts and extensive benefits.

Network Address Translation (NAT) – The Digital Cloak for Your Network

Our first installment explores the crucial role of Network Address Translation (NAT). Unlike a traditional traffic filter, NAT acts as a digital cloak for devices on your private network. It hides their actual IP addresses, preventing direct access from the internet. This protection works by modifying the source or destination IP addresses of data packets traveling through your router or firewall.

Understanding Private IP Addresses

The Internet Engineering Task Force (IETF) in RFC1918 defines three private IP address ranges that are non-routable over the public internet:  –  (  /8 prefix) –  (  /12 prefix) – (  /16 prefix)

Using these ranges for server and device numbering ensures their IPs remain inaccessible from the public internet, necessitating the ability to translate private to public IPs.

The NAT Analogy

Think of this in terms of your office phone system. Each desk phone likely has a public number for external calls. But internally, colleagues use extension numbers to reach each other. The phone system acts like a NAT table, managing the connection between public numbers and internal extensions.

How NAT Works with Firewalls

Similarly, firewalls maintain a NAT table that tracks assignments of public IP addresses to private IP addresses on your network. Each device receives a private IP address (often through Static NAT, a fixed table linking public and private addresses).

However, there might be situations where a server on your network needs to initiate outgoing connections, like downloading patch updates, but doesn’t require incoming communication. Firewalls can dynamically track these internal IPs without assigned public addresses. This allows the server to initiate communication while the firewall translates the private IP for the outgoing traffic.

HorizonIQ: Your Partner in Firewall Management

HorizonIQ, equipped with a skilled technical team, offers consultation and maintenance of your NAT table within managed firewalls. Understanding NAT’s nuances is pivotal for fortifying internet security, and HorizonIQ stands ready to provide expert guidance tailored to your needs.

Stay tuned for further installments in this series where we delve deeper into firewalls and their functionalities, empowering you to make informed decisions about your network security. HorizonIQ is committed to helping you understand the technology that safeguards your valuable digital assets.

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About Author

Paul Painter

Director, Solutions Engineering

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