Which function does Network Address Translation perform?

Network Address Translation (NAT) primarily functions to translate private IP addresses into a public IP address. This is essential for enabling devices on a local network, which typically use private IP addresses (not routable on the internet), to communicate with external networks, such as the internet. When a device within a private network sends a request to the internet, NAT modifies the originating private IP address to a public IP address, allowing the response to return to the correct device within the network.

The use of NAT helps conserve the limited availability of public IP addresses and enhances security by masking the internal network structure. Devices within the private network can communicate with each other using private addresses without exposing those addresses externally. Additionally, NAT keeps a translation table that tracks these mappings, which is critical for returning traffic to the correct internal device after it has been relayed through the single public IP address.

The other options reflect different functionalities. Automatically assigning IP addresses pertains to DHCP (Dynamic Host Configuration Protocol), which handles the assignment of IP addresses to devices within a network. Error reporting and diagnostics relate to network monitoring tools that help identify and troubleshoot issues. Monitoring network traffic involves analyzing the flow of data and ensuring proper utilization of resources, which is not a function performed by NAT itself.