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What is NAT?

NAT (Network Address Translation) is a technique of changing the source and destination IP addresses and ports. Address translation low the need for IPv4 public addresses and hides private network address ranges. The process is generally done by routers or firewalls.

There are three types of address translation:

1. Static NAT – it is the process of translates one private IP address into a public one and public IP address is always the same.

2. Dynamic NAT – in which private IP addresses are mapped to the pool of public IP addresses.

3. Port Address Translation (PAT) – it is define as the process of one public IP address is used for each internal devices, but a different port is assigned to each private IP address. Also known as NAT Overload.

An example will help you understand the concept.

Computer A request a web page through an Internet server. Because Computer A uses private IP addressing, the source address of the request has to be changed by the router because private IP addresses are not routable on the Internet. Router receives the request, changes the source IP address to its public IP address and sends the packet to server. Server receives the packet and replies to router. Router receives the packet, changes the destination IP addresses to the private IP address of Computer A and sends the packet to Computer A.

 

 

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