NAT, which stands for Network Address Translation, is a process used in computer networks to remap an IP address used within a private network to another known IP address within a public network.

NAT is commonly used on routers to allow multiple devices on a private network to access the Internet using a single public IP address.

This not only helps preserve public IP addresses (which are limited), but also adds a level of security by hiding internal network IP addresses from external devices.

How NAT Works

How NAT works can be broken down into the following basic steps:

1. Private Address Assignment: Within a local network, devices are assigned private IP addresses. These addresses are only valid within the local network and cannot be used directly to communicate with devices outside this network.
2. Internet Access Request: When a device within the local network tries to access the Internet, its request is sent to the router.
3. Address Translation: The router, using NAT, translates the private IP address of the source device on the local network to the public IP address of the router before sending the request to the Internet. For the rest of the Internet, it appears that the request originated on the router.
4. Session Tracking: NAT keeps a record of all outgoing connections so that when data returns from the Internet, it can direct the response to the correct device on the local network, using stored session information to reverse IP address translation.

NAT types

There are several types of NAT, including:

• Static NAT: Assigns a public IP address to a specific private IP address permanently. This is useful for services that need to be accessible from the outside, such as web servers.
• Dynamic NAT: Maps a public IP address from a pool of available addresses to a private IP address, but only while the device is active. When the device goes offline, the public IP address can be assigned to another device.
• PAT (Port Address Translation) o Overloaded NAT: Allows multiple devices on a private network to communicate with the Internet using a single public IP address, differentiating sessions by port number. This is the most common type of NAT, allowing efficient use of limited public IP addresses.

NAT Benefits

• Conservation of IP Addresses: Allows efficient use of a limited number of public IP addresses.
• Security: By hiding internal IP addresses, NAT provides an additional level of security since external devices cannot directly address a specific device within the private network.
• Flexibility and Scalability: Makes it easy to add more devices to the network without needing to assign additional public IP addresses.

NAT is a crucial component in modern network design and operation, enabling global communication between countless devices while managing IP address shortages and improving network security.