What is the function of a router’s NAT?

The function of a router's Network Address Translation (NAT) is to allow multiple devices on a local network to share a single public IP address. This is particularly important because there is a limited number of public IP addresses available. NAT operates by modifying the IP headers in packets as they pass through the router, enabling the internal devices—each with their own unique private IP address—to communicate over the internet while appearing as a single entity to external networks.

When a device sends data to the internet, NAT replaces the private IP address in the packets with the public IP address of the router. Conversely, when data is returned from the internet, NAT translates the public IP address back to the corresponding private IP address of the appropriate device on the local network. This not only conserves the limited number of available public IP addresses but also adds a layer of security, as internal IP addresses are not visible to the outside world.

Understanding NAT is crucial for network configuration and management, particularly in environments where multiple devices require internet access but must operate under a single public IP address.