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How NAT Traversal in VPNs?

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  • Difficulty Level : Expert
  • Last Updated : 23 Mar, 2022

NAT Traversal stands for Network Address Translation Traversal. This type of traversal method is used in web technologies to manage and process all the IP addresses while the data is being transferred through the IPSec tunnel for the translation-related issues that it faced in the data transmission. It helps to face the challenges in the data transfer which are caused during the data transmission in the IPSec tunnel. The NAT traversal is also known by the name of UDP Encapsulation. It works in the following ways:

  1. It detects the number of devices that are connected to the IPSec tunnel in the network. It senses the devices in data path connection of the devices using the User Datagram Protocol (UDP) encapsulation to IPsec data packets.
  2. The User datagram protocol network helps to produce large-scale data translations so that they can communicate between their peer nodes of the computer by disabling the IKE and the ESP traffic by using the User datagram protocol network.

Purpose of NAT-Traversal:

The main purpose of the Network Address Translation Traversal (NAT) is to allow the multiple devices connected to a network on the Internet or a small Local Area Network (LAN) to be able to map to a single IP address in order to save the IP addresses. It associates a large number of 4-5 devices that are connected to the same network on the Internet and gives them the same IP addresses to all of them so that it wouldn’t be difficult to identify the network used by these devices and also to avoid the wastage of IP addresses by providing different IP addresses to different devices connected on a network.

Types of NAT:

There are basically two broad criteria of classification of Network Address Translation Traversal (NAT). They are as follows:-

  1. Static NAT: Static Network Address Translation Traversal is a type of network traversal in which there exists an essential relationship between the public and the private IP addresses that have the ability to support both the inbound and the outbound connections of the IPsec tunnel.
  2. Dynamic NAT: Dynamic Network Address Translation Traversal allows the relationship to exist between multiple layers of the networking nodes in the IPsec tunnel as compared to the single layer of the relationship between the networking nodes in the static NAT. The main disadvantage of the Dynamic NAT is that it only supports the outgoing connections of the IPSec tunnel and not the inbound connections of the IPSec.

Working of NAT:

The Network Address Translation Traversal (NAT) works by encrypting the headers and payloads in the file by using the encapsulation of the User Datagram Protocol (UDP). It maintains the authenticity and integrity of the data transmission in the IPSec tunnel. It performs the operation by first encapsulating the Network Address Translation Traversal (NAT) header file using the User Datagram Protocol (UDP) and then the IPsec tunnel ESP header file.

The Network Address Translation Traversal (NAT) basically processes the encapsulation of the data which is transferred between two computers that are using the VPNs (Virtual Private Network). It performs hashing by generating the hashing function on the payload and the header file of the data in the IPSec tunnel using the VPNs. It then transfers the data packets in the IPSec using the tunnel or the transport mode of data transfer depending on the situation.

The Network Address Translation Traversal (NAT) is supported by those devices only that include strong firewall security for the users. It manages both the incoming and the outgoing data from the computer and scans all the data packets regularly to avoid any incident. It successfully manages all the obstacles with the help of dynamic destination NAT. It is most commonly used in places where it wants the users to connect to a minimum number of IP addresses being used. It maps and connects a large number of devices connected to IPSec to the same IP address to avoid any network traffic.



 Configuration of NAT-Traversal:

To configure the Network Address Translation Traversal (NAT) for the implementing IPsec tunnel we make sure that all the VPNs (Virtual private network) in a particular set of connected devices remain private and encrypted while data transmission using IPsec so that the other network traffic gets diverted to the servers where there is no network congestion. It is configured in such a way that to maintain the integrity of the IPsec tunnel, the NAT Traversal performs encapsulation using UDP hashing.

Tools used in NAT:

There are a large variety of tools used in the Network Address Translation Traversal (NAT) for implementing and deploying purposes. They are as follows:

  1. UDP port number 500
  2. IPSec Network Address Translation Traversal (NAT) port 4500
  3. Encapsulating Security Payload (ESP) – IPSec protocol number 50
  4. Authentication Header(AH) – IPSec protocol number 51

The Network Address Translation Traversal (NAT) ensures that all the IPsec tunnels make proper use of the VPNs (Virtual Private Network) to disable situations like network traffic at any time. Also, it must check and secure each data packet being transferred across the firewall using the User datagram protocol (UDP) and the Encapsulating Security Payload (ESP) for the authenticity and integrity of data in each data packet.

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