what does nat mean in networking

What Does NAT Mean In Networking? A Comprehensive Guide For Beginners

You may be familiar with the term NAT if you work in the field of computer networking. However, “What Does NAT Mean in Networking?” IT Exams will examine its definition, operation, and significance in networking in more detail in this article. What Does NAT Mean In Networking? IP address conservation is the goal of Network […]

April 10, 2023

You may be familiar with the term NAT if you work in the field of computer networking. However, “What Does NAT Mean in Networking?” IT Exams will examine its definition, operation, and significance in networking in more detail in this article.

What Does NAT Mean In Networking?

what does nat mean in networking

IP address conservation is the goal of Network Address Translation (NAT). It makes it possible for private IP networks to connect to the Internet using unregistered IP addresses. Before packets are routed to another network, NAT acts on a router, often linking two networks, and converts the private (not globally unique) addresses in the internal network into lawful addresses.

NAT may be set up to only advertise one address to the outside world for the whole network as part of this functionality. By essentially concealing the whole internal network behind one address, this boosts security. NAT is frequently used in contexts with remote access because it provides the combined benefits of security and address conservation.

How Does NAT Work?

what does nat mean in networking

The internal network and the external network are the two local networks that a NAT chooses as its gateways. Typically, IP addresses are allocated to systems on the internal network that cannot be routed to outside networks (such those in the block).

The gateway has a few externally valid IP addresses assigned to it. The gateway simulates outbound traffic from an inside system as originating from one of the legitimate external addresses. It redirects incoming traffic intended for a legitimate external address to the appropriate internal system.
This promotes security. The option to qualify or verify incoming streams and match them to outgoing requests, for example, is provided by the need that every incoming and outgoing request go through a translation process.

By reducing the number of globally valid IP addresses a business requires, NAT has significantly contributed to extending the usable life of IPv4 in conjunction with Classless Inter-Domain Routing (CIDR). In general, NAT is explained in IETF RFC 1631.

How Many Types Of NAT Are There?

what does nat mean in networking

There are several types of NAT, including:

Static NAT

For servers that need to be able to access the internet, including web servers, mail servers, and FTP servers, static NAT, which creates a one-to-one mapping between a private IP address and a public IP address, is frequently used. In order to access the server from internet clients while keeping the private IP address hidden, it is necessary to associate a private IP address with a public one. This increases the security of the local network against prospective intruders. Typically using the router’s settings interface, configuring Static NAT on a NAT router entails manually providing the mapping between the private and public IP addresses. To allow inbound traffic to reach the server, administrators can specify port forwarding rules, provide the server’s private IP address, and choose the appropriate public IP address.

Dynamic NAT

For outbound connections started by devices on the local network, dynamic NAT, as opposed to static NAT, dynamically assigns public IP addresses from a smaller pool to a range of private IP addresses. The NAT router chooses an accessible public IP address from the pool when a device makes a connection and maps it to the device’s private IP address to allow communication with the distant server. The router returns the mapped public IP address to the pool for use by other devices when the conversation is over. When there are more devices than public IP addresses and when fixed public IP addresses are not required, this strategy is frequently utilized. By distributing public IP addresses across several devices, it efficiently conserves them. Administrators can set the pool of public IP addresses to utilize as well as the range of private IP addresses to map when configuring dynamic NAT on a router. Additionally, the router may be configured to distribute public IP addresses using a round-robin algorithm or a first-come, first-served method.

Port Address Translation (PAT)

A type of NAT called Port Address Translation (PAT), also known as NAPT, allows many devices on a local network to share a single public IP address by using various ports. The NAT router assigns a distinct source port number and links it to the router’s public IP address whenever a device on the local network starts an outgoing connection. As a result, when a response is received from the internet, the NAT router uses the source port number to identify the right device on the local network to forward the response to, guaranteeing a unique mapping for each device. When there are more devices on a local network than there are public IP addresses accessible and when devices don’t need a fixed public IP, this capability is especially helpful. PAT helps save these resources by efficiently distributing public IP addresses across several devices. The pool of accessible source port numbers and the range of private IP addresses to be mapped must be specified in order to configure PAT on a NAT router. Additionally, the router can be configured to use a round-robin mechanism or a first-come, first-served method for allocating source port numbers to devices.

How Is NAT Important In Networking?

what does nat mean in networking

NAT is important in networking for a number of reasons. By enabling several devices connected to a local network to share a single public IP address, it first makes it possible to preserve the IP address pool’s limited supply of public IP addresses. Additionally, NAT adds an extra degree of protection by hiding private IP addresses from prospective internet intruders, preventing illegal access, and defending against new cyber threats. Additionally, NAT enables communication and smooth data exchange between devices with globally routable IP addresses on the Internet and those on private networks with non-routable IP addresses. Additionally, NAT gives network managers flexibility in network design by permitting changes to the local network’s topology without having an impact on the public IP address allocations. This allows for adaptation to changing business requirements while maximizing network performance. Finally, PAT, a kind of NAT, allows numerous devices to access the internet using a single public IP address while keeping distinct mappings depending on source port numbers, enabling effective load balancing and optimal usage of network resources.

What Are Some Common NAT Issues?

what does nat mean in networking

Despite the simplicity of the NAT general applications described so far, the underlying NAT functions might be more complex due to the following two reasons:

  • General IP and TCP header processing
  • The nature of some protocols and applications

The significance of any of the other elements, particularly the checksum, can vary if the content of an IP address or TCP port is modified. The IP address or information based on the IP address is carried by several protocols and applications in their data fields. The program could stop working if an IP address in the header is changed since it might modify how the wrapped data is understood. The most frequent concerns relating to NAT functioning are examined in this section.

Header Checksums

The checksum of an IP packet is computed across the whole header. As a result, if the source or destination IP address, or both, change, the checksum must be redone. The checksum in the TCP header is the same way. This number is computed over the TCP header and payload, as well as a pseudo-header including the source and destination IP addresses. As a result, whenever an IP address or port number changes, the TCP checksum must likewise update. Cisco’s NAT does these checksum recalculations.


Remember from the “NAT and Virtual Servers” section that NAT may be used to translate to multiple local addresses dependent on the target port. A packet with the destination port number 25 may be translated to a certain IL address, however packets with other destination port numbers can be translated to other addresses. But what if the packet meant for port 25 becomes fragmented elsewhere along the network before reaching the NAT? The TCP or UDP header, which contains the source and destination port numbers, is only included in the first segment. If that fragment is simply translated and transmitted, the NAT has no way of knowing if following pieces must also be translated.

IP offers no assurances about packet delivery order. As a result, the initial fragment may not even reach at the NAT before further pieces. NAT must be designed to handle such scenarios.

Cisco’s NAT maintains stateful fragment information. When the first fragment is translated, the information is saved so that following pieces can be translated in the same manner. If a fragment comes before the first, the NAT is forced to keep the fragment until the first arrives and can be analyzed.


As you shall see in a moment, many programs include IP address information in their data fields that may be changed by Cisco’s NAT. However, if the data fields are encrypted, NAT is unable to read the data. Therefore, neither the IP addresses nor any information generated from them (such the TCP header checksum) can be encrypted for NAT to work.

Virtual private networks (VPNs) employing, for instance, IPSec, are a further issue. When using specific IPSec modes, if an IPSec packet contains a changing IP address, the IPSec is rendered useless and the VPN is disrupted. When using encryption of any kind, the NAT must be situated on the secure side as opposed to the encrypted way.


Because NAT conceals the specifics of the internal network, some people see it as a component of a security strategy. A translated host can show up online with one address one day and a different address the next. But at best, this is pretty inadequate security. Any motivated and skilled attacker will succeed despite NAT, which may slow him down by making him play a kind of IP address shell game in order to target a specific host. Even worse, NAT does nothing to stop attacks like denial of service or session hijacking, which are rather popular.

Protocol Issues

NAT ought to be transparent to the end systems sending packets via it. However, a large number of programs—both for profit programs and programs that use the TCP/IP protocol family—require IP addresses. The data field may contain information that is dependent on an IP address or may carry an IP address directly. The program crashes if NAT translates an address in the IP header without taking into account how it will affect the contents.

3 Benefits of using NAT for security purposes

  1. The use of NAT for security purposes has several benefits. First, it can help to protect devices on the private network from direct attacks and unauthorized access from external sources. By hiding private IP addresses, NAT makes it more difficult for attackers to target specific devices and services on the private network.
  2. Second, NAT can provide a degree of privacy for devices on the private network. By hiding private IP addresses, NAT prevents external devices and services from tracking and monitoring the activity of devices on the private network.
  3. Finally, NAT can ease network management and lower the possibility of setup mistakes. NAT can simplify network routing, simplify management of network traffic, and provide a single point of entrance and exit for data between the private network and the public internet.


what does nat mean in networking

What is NAT in simple terms?

Network address translation is referred to as NAT. It’s a technique for translating several private addresses within a local network to a public IP address before sending the data over the internet. Both most household routers and organizations that need many devices to share a single IP address utilize NAT.

Can NAT be disabled?

As it might expose your internet modem to outside infiltration and pose a security risk, we advise against disabling NAT unless specifically told to do so by a trained expert.

Is NAT the same as a firewall?

With only a “default deny” policy for incoming packets that are not requested, NAT functions as a firewall.

Machines outside of a NAT box cannot transmit IP packets directly to them since they are not directly accessible (often because they have private IP addresses). Any packets will be routed to the NAT box’s address instead, and the NAT box will check its records to identify which outgoing packet each incoming packet is a reply to and will then determine which internal address the packet should be sent to. The NAT box discards the packet if it is not a response to an outgoing packet and there is no record that matches it.

Can NAT be used with IPv6?

NAT is not used by Pv6 mostly because it is not required! Every device may have a unique IPv6 address because there are far more of them available (340,282,366,920,938,463,463,374,607,431,768,211,456 vs. 4294967296, albeit not all in each group are useable!). NATv6 has a standard, although it is rarely utilized.

If a machine uses a constant address online, it may be monitored and perhaps recognized, which is one problem with not employing NAT. Fortunately, that can be fixed. Use a temporary address that updates periodically as a workaround. This prevents online watchers from seeing and following a certain address. The Internet service provider and organization will be reflected in the first portion of the temporary address, and the last part will be modified. The size of the organization will determine how big each of those components is. The final 64 bits of the address in my case change.

Final Words

In a nutshell, NAT is an essential networking method that enables private network devices to connect with those on a public network while hiding their private IP addresses. A method for protecting IP addresses, preventing IP address conflicts, and boosting network security is provided by NAT. Static and dynamic NAT are two types of NAT that may be used with port forwarding to enable external devices to connect to private network devices. Is it appropriate for you to ask, “What does NAT mean in networking?” You may more fully enjoy something now that you understand what it is and why it is important. You may enhance network performance for your devices and network security by using NAT.