How does Network Address Translation (NAT) function?

Network Address Translation (NAT) functions by allowing multiple devices on a local network to share a single public IP address when accessing the internet. This is essential for managing the limited number of available IP addresses and enhances security by obscuring internal IP addresses from external networks.

When devices on a private network need to communicate with the outside world, NAT modifies the source IP address of outgoing packets to the public IP address assigned to the router and tracks this translation in a table. When a response is received from the internet, NAT uses this table to route the response back to the correct internal device. This way, it effectively separates internal IP addresses, which are not routable on the internet, from the external addresses used for internet communication.

In contrast, the other choices refer to different functionalities in networking: encryption pertains to securing data, filtering at the application layer involves examining traffic at a higher protocol level, and intrusion detection/prevention focuses on monitoring and protecting against unauthorized access. None of these accurately describe the primary function of NAT, which is to manage and separate IP addresses for both internal networks and the external internet.