Network Address Port Translation

What Does Network Address Port Translation Mean?

Network address port translation (NAPT) is a technique in which port numbers and private Internet Protocol (IP) addresses are mapped from multiple internal hosts to one public IP address.

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It is a type of network address translation (NAT) technology that extends capabilities by translating and mapping port numbers, in addition to the IP address, when communicating with an external network.

Techopedia Explains Network Address Port Translation

NAPT maps Transmission Control Protocol/User Datagram Protocol (TCP/UDP) port numbers and IP addresses of local devices with registered, public IP addresses and corresponding TCP/UDP ports. NAPT uses the same public IP address to enable the connection of multiple internal hosts with external networks or the Internet.

NAPT is usually configured on a routing device, like a router. Each internal host requesting connection to an external network passes through the NAPT device, which changes the host device’s IP address and port number to a pool of public IP addresses and port numbers. For example, a device that requests access may have the IP address 10.0.0.1 and port 5678. When its packets leave the NAPT device, its IP address is 203.22.11.20 – or any available public IP address – and port 7650.

The NAT device or router usually is configured with or assigned the public IP address, allowing multiple local hosts to have the same IP address with different port numbers in order to access Internet/external networks.

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Margaret Rouse is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical, business audience. Over the past twenty years her explanations have appeared on TechTarget websites and she's been cited as an authority in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine and Discovery Magazine.Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages. If you have a suggestion for a new definition or how to improve a technical explanation, please email Margaret or contact her…