Which statement best describes NAT’s primary function in a network?

• A. NAT encrypts all outbound traffic by default.
• B. NAT assigns public IP addresses to devices automatically.
• C. NAT prevents inbound traffic from the internet by default.
• D. NAT allows multiple devices on a local network to share a single public IP address.

Answer: (D)

NAT's primary function is to allow multiple devices on a local network to share a single public IP address when accessing the internet. It does this by translating each device’s private IP address (and its port) to the router’s public IP for outbound traffic, while keeping a translation table so return traffic can be mapped back to the correct internal device. When many devices use one public IP, different source ports help distinguish their connections—this is often called Port Address Translation. This sharing of a single public IP conserves IPv4 addresses and enables devices on a private network to reach external destinations.

Other statements miss the core idea: NAT doesn’t encrypt traffic by default, it doesn’t automatically assign public IPs to each device, and while NAT can obscure internal addresses, it isn’t a true firewall and doesn’t inherently block inbound traffic without specific rules or configuration.