What Is Network Address Translation?

Date First Published: 3rd March 2022

Topic: Computer Networking

Subtopic: Network Services

Article Type: Computer Terms & Definitions

Difficulty Level: 8/10

Learn more about what network address translation is in this article.

Network address translation, often shortened to NAT, is a process that was developed by Cisco that translates the IP address of computers on a local network to a single IP address. The router that links the computers to the internet often uses this address. NAT assigns a public IP address to a computer inside a private network.

Note:

NAT is most commonly used by organisations and companies for putting a limit on the number of public IP addresses that are necessary to be used for the purpose of security and economy.

NAT is often configured to translate unregistered (local) IP addresses to registered IP addresses. The unregistered IP addresses are ‘mapped’ to the registered IP addresses. For example, NAT could be configured to translate the unregistered IP address: ‘123.122.12.10’ to a registered IP address: ‘123.121.15.12’. A diagram of NAT can be seen below.

Types Of NAT

• Static NAT - Translates an unregistered IP address to a registered IP address. When static NAT is used, a computer will always translate to the exact same registered IP address.
• Dynamic NAT - Translates an unregistered IP address to a registered IP address from a group of registered IP addresses. Computers with a certain IP address will translate to the first available IP address within a range when dynamic NAT is used.
• Overloading - Also known as PAT (Port Address Translation) or single-level NAT, overloading is a type of dynamic NAT that translates multiple unregistered IP addresses to a single registered IP address through the use of different ports. Computers have a different port number assignment.
• Overlapping - When the IP addresses used on an internal network are registered IP addresses that are in use by another network. Internal IP ranges may be a registered range of another network. IP addresses are translated for the purpose of avoiding conflict with another network. The registered global IP addresses will be translated back to the unregistered local IP addresses when information is sent to the internal network.

The internal network is commonly referred to as a LAN, also known as a stub domain (not to be confused with a subdomain). Stub domains are LANs that use IP addresses internally. The traffic of stub domains is often local and does not travel outside of the internal network, although stub domains can include both registered and unregistered IP addresses.

Advantages And Disadvantages Of NAT

• It provides protection for registered IP addresses.
• It provides privacy as the IP address of the device that is sending and receiving traffic will be hidden.
• It prevents the reduction of available IP addresses since private IP addresses are used.
• It enhances the security of private IP addresses by keeping internal addressing private from the external network.

• Certain applications will not work when NAT is enabled.
• It can mess up tunnelling protocols, such as IPsec .