What is the function of NAT?

NAT, or Network Address Translation, primarily serves the function of allowing multiple devices within a private network to share a single public IP address. This is particularly important in situations where there is a limited number of available public IP addresses, as it helps in conserving them. With NAT, each device on a local network can communicate with external networks (like the internet) while using private IP addresses that are not routable on the public internet. The NAT device keeps track of these private IP addresses and translates them to the single public IP address when packets need to be sent out, and vice versa for incoming packets. This functionality allows for both efficient use of IP addresses and adds a layer of security by not exposing every device on the network directly to the internet.

While automatic assignment of IP addresses pertains to DHCP, filtering traffic by MAC addresses is more related to network switches or access control lists, and securing connections for remote users correlates with VPN technologies. Therefore, these options do not align with NAT's primary function.