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The Difference Between NAT (Network Address Translation) vs PAT (Port Address Translation)

NAT (Network Address Translation)

Network Address Translation (NAT) basically connects two networks and map the private (inside local) addresses into public addresses (inside global). Here the term inside local signifies that the host address belongs to an internal network and not assigned by Network Information Center or service provider. And the inside global means that the address is a licit address assigned by the NIC or service provider and it also represents one or more inside local addresses to the outside world.

A NAT device helps in increasing the security as it can prevent an outside attacker even to find the local network. This is because of local addressing scheme is not contiguous with the standard IP address space used worldwide.

NAT can be of three types :

  • Static NAT – In this type of NAT a local address is mapped to a global address, and there exists a one-to-one relationship. Static NAT is useful when a host requires a consistent address, which must be accessed from the internet. For example, enterprise servers or networking devices.

  • Dynamic NAT – Dynamic NAT allows unregistered private IP address to be translated into registered public IP address from a pool of public IP addresses.

  • PAT/ NAT Overloading/IP masquerading – PAT is most popular type among the three types. It is a variant of Dynamic NAT and is similar to it, but it maps multiple private IP addresses to a single public IP address by making use of ports.


  • NAT preserves the registered public addresses and slows down the depletion of the IP address space.

  • Occurrence of address overlap significantly reduces.

  • Increases flexibility of the connection establishment.

  • Removes the process of address renumbering at the time of changing network.


  • Switching path delays are the outcome of the translation.

  • Lack of end-to-end traceability.

  • Certain applications are not compatible with NAT.

PAT (Port Address Translation)

Port Address Translation (PAT) is a type of Dynamic NAT through which address translation can be configured at the port level, and the remaining IP address usage is also optimized. PAT maps multiple source local addresses and ports to a single global IP address and port from a pool of IP addresses that are routable on the destination network. Here the interface IP address is used in combination with the port number and multiple hosts could have same IP address because the port number is unique.

PAT helps in optimum utilization of IP address space by way of allocating one dedicated IP address for the organization and internally uses IP addresses as per the need. PAT is the extension of the NAT


  • Conserve IP addresses by assigning single public IP to a group of hosts with the help of the different port numbers.

  • Lessens the vulnerabilities or security attacks as the private address prevent the public address from being exposed.


  • More than one same type of public services cannot be executed with a single IP address in PAT.

  • Number of entries are limited in the internal table for keeping the tracks of the connections.

Difference Between NAT and PAT


NAT Translates the private local IP address to the public global IP address.

Similar to NAT it also translates the private IP addresses of an internal network to the public IP address with the help of Port numbers.

Superset of PAT

Variant of NAT (form of a Dynamic NAT).

It uses IPv4 address

It uses IPv4 addresses along with the port number.

There are three types of NAT 1. Static NAT 2. Dynamic NAT 3. PAT/ NAT Overloading/IP masquerading

There are two types of PAT 1. Static PAT

2. Overloaded PAT

Also Read:

AMQP (Advanced Messaging Queuing Protocol) vs MQTT(Messaging Queuing Telemetry Transport)

ARP(Address Resolution Protocol) vs RARP (Reverse Address Resolution Protocol)

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