Network Address Translation and its Types

NAT as is states Network Address Translation, it used for hiding internal private IP with public IP.

NAT has its types based on its functionality

• Static NAT
• Dynamic NAT
• PAT (Port Address Translation)

 Static NAT (Network Address Translation) - Static NAT (Network Address Translation) is one-to-one mapping of a private IP address to a public IP address. Static NAT (Network Address Translation) is useful when a network device inside a private network needs to be accessible from internet.

Here in Static NAT, there is one to one translation of IP Address. Single Private IP (Inside Local IP) is translated to Single Public IP (Outside Public IP). Static NAT is costlier as Public IPs are brought from Service Provider. Also the Static NAT technique utilizes the Global IP scheme.

NAT And its Types

Dynamic NAT (Network Address Translation) - Dynamic NAT can be defined as mapping of a private IP address to a public IP address from a group of public IP addresses called as NAT pool. Dynamic NAT establishes a one-to-one mapping between a private IP address to a public IP address. Here the public IP address is taken from the pool of IP addresses configured on the end NAT router. The public to private mapping may vary based on the available public IP address in NAT pool.

Here in Dynamic NAT, we use group of Public IP for connecting the internet. All inside Private IPs reaches Internet through NAT public Pool. It is used for dividing the traffic going to network, like for inside web servers can be reachable through different NAT Public IP and for users reaching internet use different NAT IP.

PAT (Port Address Translation) - Port Address Translation (PAT) is another type of dynamic NAT which can map multiple private IP addresses to a single public IP address by using a technology known as Port Address Translation.

Here when a client from inside network communicate to a host in the internet, the router changes the source port (TCP or UDP) number with another port number. These port mappings are kept in a table. When the router receive from internet, it will refer the table which keep the port mappings and forward the data packet to the original sender.