This page on NAT vs PAT describes difference between NAT and PAT.

NAT stands for Network Address Translation and PAT stands for Port Address Translation.

A network address translation device obscures all details of the computers connected to the local network. NAT device acts as gateway for all the computers. Behind the NAT device, local network can use any network address space. NAT device acts as proxy for the local network on the internet.


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.


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

Say for example there are two computers trying for access to the internet. As per PAT say computer 'A' tries to connect, this time computer-A will be assigned with one port number and IP address. At this time another computerB tries for the connection will be given the same local IP address but the different port number. This way one can conserve the IP address space by way of identifying the received packet with the use of port number and local IP address. .


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