Which NAT type maps many private addresses to a single public address using ports?

• A. Static NAT maps a fixed private address to a public address.
• B. Dynamic NAT uses a pool of public addresses.
• C. PAT (Port Address Translation) maps many private addresses to a single public address using ports.
• D. NAT translates addresses in both directions without port translation.

Answer: (C)

Port Address Translation lets many private devices share a single public IP by using port numbers to distinguish each connection. When an inside device talks to the internet, the router changes the source IP to the public IP and assigns a unique source port for that connection. The router keeps a table that maps the internal IP:port to the external IP:port. When responses return, it uses the destination port to route the traffic back to the correct inside device, reversing the translation. This multiplexing—one public address with many different ports—is why this method is able to support numerous internal hosts with only one public address. By contrast, static NAT maps one private address to one public address with no port sharing, and dynamic NAT uses a pool of public addresses without multiplexing all inside addresses onto a single public IP. The idea of translating addresses in both directions without port translation doesn’t fit the common PAT behavior, which relies on ports to distinguish multiple internal hosts.