What is Network Address Translation?

What is Network Address Translation

Network address translation conserves IP addresses by enabling private devices to connect to the internet using unique registered global addresses instead of public ones, thus providing greater security.

Static or dynamic NAT both require organizations to invest in large pools of public IP addresses; this article will focus on dynamic NAT.

What is NAT?

Network address translation allows one device to represent multiple devices on a private network. It works by having routers or firewalls convert private IP addresses of devices into their public equivalents; then when data is sent out over the Internet by this device it arrives with its source IP hidden so as to reduce cyberattack vulnerabilities and make for easier management of the network overall.

As networks expand, it becomes ever more crucial to keep them secure and manageable. One method for doing this is using network address translation (NAT), which helps protect devices on a network from outsiders trying to gain entry and also helps reduce demand for global IP addresses, especially as we transition away from IPv4 toward IPv6.

Static Network Address Translation (SNAT) is one of the more prevalent NAT types, used to match private IP addresses to registered unique external addresses. When data requests arrive from the Internet, this type of NAT switches them for its own public address and stores it in a translation table; additionally it filters packets to prevent unwanted or harmful traffic.

Dynamic Network Address Translation (DNAT) is another type of NAT that can enhance security by replacing unregistered IP addresses with unique ones, filter packets and limit their size as well as apply security protocols to protect local networks from outside threats. It’s often seen in enterprise environments to maintain performance by keeping traffic localized to one area of a local network.

Dynamic NAT can present some disadvantages; in particular, supporting higher-level protocols requiring the reassembling of fragmented data packets can be challenging and SSL encryption causes issues when browsing websites with dynamic NAT. On the plus side, however, there are other solutions which provide additional functionality while protecting high-level protocols better, such as Fortinet’s next-generation firewalls.

What is NAT’s Purpose?

Network Address Translation (NAT) is used to reduce the number of IP addresses needed on public networks while also protecting private devices from attackers by hiding their internal network identities. NAT works by assigning each device on a private network a unique IP address that only other devices within that LAN (local area network) can access; then translating those private IPs into one global public IP address so each can gain Internet connectivity.

When devices on one LAN send data to devices on another LAN, information is transmitted in packets containing both source and destination IP addresses as well as port numbers. Once received at a router, its use of destination port numbers determines where to route them; then when reaching its final destination without knowing its private IP address. A NAT firewall then modifies both its IP address and port information so the packet reaches its final destination without knowing who sent it or receiving its private IP address information from that device on its way there.

If every device on a private network was assigned its own public IP address, we would quickly run out of global addresses. With NAT, multiple devices on one network can share one public IP address thereby decreasing our need for IP addresses while saving money through RFC 1918 addresses.

There are two forms of Network Address Translation (NAT), static and dynamic. Static NAT works by translating the same private address over time to its equivalent public address, while dynamic NAT utilizes available global IP addresses as necessary to match inside and outside IP addresses when required. Port Address Translation, or PAT, provides additional functionality by translating multiple private IP addresses onto one port outside.

NAT gateways or servers, the routers that perform port address translation, are commonly integrated into larger organizations’ firewalls to increase security by restricting what data outsiders can access from within, while at the same time decreasing traffic through their firewall. Network address translation helps increase security by restricting who can gain access to confidential files within, as well as improving performance by decreasing how often traffic passes over it.

What is NAT’s Function?

Simply put, Network Address Translation (NAT) serves as an intermediary between local networks and the larger Internet. A router or firewall containing this function assigns one IP address per host connected to their internal network and converts these private addresses to unique public IP addresses attached to its gateway – this allows devices to send data through without using up all their reserved public IP addresses.

When an Internet-facing device on a private network attempts to establish contact with another computer or service on the Internet, they send a packet with its destination IP address and port number for translation by NAT device. Once translated, this entry creates an entry in its translation table which replaces original source IP with external or global IP and adds their unique port number in packet header.

A packet is then distributed onto the Internet with its new IP header that tells its destination host where to locate the NAT device, so that they may connect with it over the Internet without being aware that their original internal source IP address has been hidden behind an internationally visible IP address (or public IP address).

There are various forms of Network Address Translation (NAT), the two most prevalent being static and dynamic NAT. Static NAT uses translation software to permanently map an unregistered IP address to one that has already been registered – often required in large organizations as any additional unique public addresses would quickly deplete their alloted pool of publicly routable addresses.

Dynamic NAT is more efficient than static NAT as it can accommodate an increased volume of traffic by dynamically mapping IP addresses. When an unregistered internal IP address transmits packets onto the Internet, an unregistered internal port number will be assigned from within its translation table to match with an available entry in its translation table and transmit that packet through. Furthermore, dynamic NAT devices track connections so as to know when changing an IP address or port back to its original state is necessary.

What is NAT’s Limitations?

Network address translation (NAT) has its limitations. As with any tool, NAT can be useful in various scenarios and is versatile enough to fit various uses – it just may not always work perfectly with every service or app, sluggish Internet speeds, and potentially lead to disruption.

There are various types of Network Address Translation (NAT), each offering their own advantages and disadvantages. One popular form is port address translation (PAT). PAT allows many private IP addresses to connect to the internet through one public IP address – typically found on routers or firewalls.

How NAT works is that its router converts IP addresses in packet headers and payloads according to an established set of rules. When devices on the inside want to communicate with outside devices, they send requests through to their NAT router, who looks at its source address to determine whether it comes from within their local or global IP addresses and then route data packets accordingly.

Utilizing Network Address Translation (NAT) can be an excellent way to conserve IPv4 address space and avoid running out. Assigning each device its own unique IPv4 address would quickly exhaust our available allocation. Instead, using NAT allows devices on private networks to share one routable IP address to access the Internet while still having distinct internal addresses.

NAT may slow the Internet because of the need to examine all incoming and outgoing data packets; this may become particularly evident with VoIP applications such as Skype and SIP which require that each data packet contains both an IP address and port number.

One solution for overcoming this limitation is using a form of NAT that uses dynamically allocated ports – commonly referred to as PAT but sometimes also called many-to-one or overload. A router uses different port numbers in this type of NAT to map multiple local IP addresses unregistered with any registry onto one registered public IP address.

Mark Funk
Mark Funk is an experienced information security specialist who works with enterprises to mature and improve their enterprise security programs. Previously, he worked as a security news reporter.