- Network address translation (NAT) is defined as the process of mapping private IP addresses to a single public IP address while information is being transferred via a router or NAT firewall.
- This article explains how NAT works and its uses and gives a few examples.
Table of Contents
- What Is Network Address Translation (NAT)?
- How Does NAT Work?
- Examples of Network Address Translation
What Is Network Address Translation (NAT)?
Network address translation (NAT) is the process of mapping private IP addresses to a single public IP address while information is being transferred via a router or NAT firewall. NAT is used by organizations with multiple devices needing access to the internet via a single public IP address.
If all the devices on a private network are configured to use the same public IP address range, the number of IP addresses required is greatly reduced, which helps conserve address space. Since NAT hides internal IP addresses and mapping information, it can also be used as a basic firewall to help protect LANs from hacking and denial-of-service (DoS) attacks.
Network Address Translation
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NAT is a very broad term that covers various types of network address translations. Listed below are some of the most common types of NATs, their benefits, downsides, and usage.
See More: What Is Local Area Network (LAN)? Definition, Types, Architecture and Best Practices
1. Static NAT
Static NAT maps a private IP address for a network device to a single public IP address. This is called static translation because the mapping is not dynamic and does not change over time.
This can be used in home networks to access smart devices or gaming consoles over the internet. While this type of NAT is highly sought-after due to the permanent mapping it establishes between private and public IP addresses, it is recommended not to opt for this type when very high security is to be maintained.
Example: If a device with a private IP address 10.0.0.0/24 is mapped to a public IP address 59.50.50.0/24 during internet access or communication over the internet, that public IP address will always be the same. As a result, any time the device communicates over the internet, its public IP address will appear as 59.50.50.0/24 and not any other.
2. Dynamic NAT
As the name suggests, dynamic NAT maps private IP addresses with a pool of public IP addresses on a first come, first served basis. Whenever a private network device needs to access the internet, an available public IP address from the pool is assigned. While this type is secure and fast, a major drawback of dynamic NAT is that the device must wait if the pool runs out of available public IP addresses.
Dynamic NAT is useful when more devices are on a private network than the available public IP addresses. This method ensures that the device(s) that wants to communicate over the internet gets assigned to an available public IP address first.
Dynamic NAT is extensively used where a high level of security is required as it completely hides private IP addresses over the internet. It is also used extensively where a group of private network devices must dynamically access the internet.
This type of NAT is suitable for use in vast enterprise networks where many private network devices must access the internet frequently per the requirements. It is also used in home networks with many connected or smart devices such as smart mobiles, connected TVs (CTVs), computers, laptops, and tablets, among others.
Example: Let’s suppose there are three devices in a private network — A, B, and C — with private IP addresses 10.0.0.1, 10.0.0.2, and 10.0.0.3, respectively. Then there is a pool of public IP addresses 200.100.50.1, 200.100.50.2, and 200.100.50.3.
Now, if device A wants to communicate with the internet first, followed by B and C, they will be assigned IP addresses 200.100.50.1, 200.100.50.2, and 200.100.50.3, respectively, on a ‘first come, first served basis.’ If a fourth device, D, wants to communicate over the internet, it must wait until a public IP address is available.
3. NAT with port address translation (PAT)
NAT with port address translation (PAT), also known as network address port translation (NAPT), allows several private network devices to share the same public IP address through multiple port numbers.
A unique port number gets assigned to each device over a private network whenever they need to communicate over the internet. During the communication, the NAT router translates the port number and the private IP address into a single port number and public IP address. As a result, multiple devices can communicate easily and fast over the internet by using a single public IP address.
PAT is applicable when multiple devices on a private network require access to the internet, but only one public IP address is available. Also, it lets the NAT router distinguish diverse devices on the private network with their unique port numbers. This, in turn, lets the devices access the internet as if they have their own public IP addresses.
PAT is widely used in home networks with connected smart devices such as smartphones, smart TVs, computers, tablets, etc., which share the same network. This type suits enterprises with a shared internet connection for all their devices.
Example: Let’s say there are three devices over a private network — A, B, and C — with private IP addresses and port numbers as 10.0.0.1 and 5000, 10.0.0.2 and 5001, and 10.0.0.3 and 5002, respectively.
A NAT router will translate these private IP addresses and port numbers into a single public IP address and different port numbers whenever these devices need to access the internet. For instance, device A can have the public IP address 200.100.50.1 and port number 6000, while the same for device B and device C can be 200.100.50.1 and 6001 and 200.100.50.1 and 6002, respectively.
See More: What Is Network Management? Definition, Key Components, and Best Practices
How Does NAT Work?
Whenever a device on a private network needs to communicate with the internet, it sends a request to the NAT router to map its private IP address with a public IP address to access the internet. As soon as the response from the internet is received, the NAT router maps the public IP address to the private IP address. Once this is done, a response to the private network device is sent.
This way, traffic between devices on the same network is hidden from each other and appears as if it were coming from outside of their local area. This allows users on different networks to communicate without having their data visible or accessible by other devices on their own networks.
How NAT Works
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The figure above shows the link between two networks when using NAT. The external network has an external interface, which connects directly with the internet, while in the internal interface (or private side), all resources are hosted on an internal network. A device within the network only needs one public IP address; the router assigns one based on its own configuration settings.
However, when someone tries accessing the computer from outside via any other device connected on either side of this link (such as another computer or smartphone), they won’t find anything but static data. This way, it hides internal IP addresses from external networks. Therefore, one need not worry about people hacking or stealing information through an open port (such as port 80).
The mapping process between private and public IP addresses in NAT occurs through NAT tables. These tables refer to data structures that are stored by the NAT router. When a private IP address requires access to the internet, it gets mapped to a public IP address to mask its identity over the internet. However, once the internet sends back the responses, the public IP address gets converted into a private IP address.
Types of NAT tables
- NAT outbound tables: These map private addresses to a public IP address while a device from a private network requests internet access.
- NAT inbound tables: These let a public IP address switch back to the original private IP address as soon as the internet responds.
Key components of a NAT table entry
- Private IP address: The original IP address of the private network device
- Public IP address: The IP address to which the private IP address gets mapped while communicating over the internet
- Protocol: The communication protocol used during the process
- Private port: The port number of the private network device
- Public port: The port number that a NAT router uses during the communication process with the internet
The mapping process
An incoming packet with a source IP address of 192.168.1.2 is received by the NAT router that looks up its NAT table and finds that it has a mapping for 192.168.1.2 to 10.6.8.6, which means packets with this source IP address will be forwarded to the local network 10.6.8.0/24, and from there to other networks in the same subnet (10.6.8.) The NAT table also contains a mapping for 192.168.1.* to 10.*.*.*, which means that any packet sent by any client that has an IP address within 192.*.*.* will be forwarded to the local network 10.*.*.*
The NAT router then forwards this packet to the destination device (10) using its own internal address space (192), which is then translated back into an external IP address for forwarding onto other networks (10).
See More: Top 10 Best Practices for Network Monitoring in 2022
Examples of Network Address Translation
Here are some of the top examples and use cases of network address translation:
NAT Examples
1. Home networks
NAT is extensively used in home networks to allow multiple smart devices such as smart mobiles, smart TVs, computers, laptops, and others to securely share a single internet connection. The NAT router maps private IP addresses to the devices on the home network. It translates these private IP addresses into a single public IP address during the sessions over the internet.
2. Office networks
NAT is widely used by small to large businesses and enterprises to give their employees internet access from their office devices securely. The NAT router assigns private IP addresses to the devices on the office network. It translates these private IP addresses into a single public IP address when communicating with the internet.
3. Virtual private networks (VPNs)
VPNs are another key use case of NAT. It allows devices on a private network to communicate over the internet with their public IP addresses. The NAT router first maps the private IP addresses to the devices on the VPN and then translates them into a public IP address during their sessions over the internet.
4. Cloud computing
NAT is used in cloud computing to let the devices on a private network communicate with the internet with their own public IP addresses. The NAT router assigns private IP addresses to the devices on the cloud network and translates these private IP addresses into a public IP address when communicating with the internet.
5. Internet of Things (IoT)
NAT is used in the Internet of Things (IoT) to let devices such as smart home devices and wearable technologies easily communicate over the internet. The NAT router assigns private IP addresses to the devices on the IoT network and translates these private IP addresses into a public IP address when communicating with the internet.
6. Wireless networks
NAT is often used in wireless networks to allow multiple devices, such as laptops and smartphones, to connect to the internet using a single public IP address.
7. Mobile networks
Network address translation is frequently used in mobile networks to allow multiple devices, such as smartphones and tablets, to connect to the internet using a single public IP address.
8. Satellite networks
NAT is often used in satellite networks to give multiple devices, such as computers and routers, access to the internet using a single public IP address.
9. Military networks
NAT is also used in military networks to allow multiple devices, such as computers and servers access the internet using a single public IP address.
Takeaway
As discussed above, NAT has unlimited use cases and benefits, from home networks to expanded office and enterprise networks. Based on the specific use case, available private network devices, and the security level to be maintained, you can pick the most suitable type of NAT.
However, you must also be aware of a few drawbacks, such as difficulties establishing a connection between external and local network devices. However, the advantages outweigh these few cons. The process of network address translation is a great way to improve your network’s security and reliability.
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