What is NAT (Network Address Translation)?

NAT (Network Address Translation) is a technique used in computer networking to translate private IP addresses within a local network to public IP addresses that can be used on the internet. It allows multiple devices within a private network to share a single public IP address, conserving the limited number of available public IP addresses.

NAT works by mapping the private IP addresses of devices within the local network to a public IP address assigned by the internet service provider (ISP). When a device from the local network sends a request to access the internet, the NAT device replaces the private IP address in the outgoing packets with the public IP address. This allows the device to communicate with external networks using the public IP address.

NAT also keeps track of the translations it performs, creating a mapping table that associates private IP addresses with their corresponding public IP addresses. This table is used to route incoming responses from external networks back to the correct device within the local network.

There are different types of NAT, including static NAT, dynamic NAT, and port address translation (PAT). Static NAT assigns a specific public IP address to a specific private IP address, while dynamic NAT assigns public IP addresses from a pool of available addresses on a first-come, first-served basis. PAT, also known as NAT overload, allows multiple devices to share a single public IP address by using different port numbers to differentiate between the devices.

Overall, NAT plays a crucial role in allowing devices within a private network to access the internet using a limited number of public IP addresses, enhancing network security and conserving IP address resources.