Which technique allows many internal hosts to share a single public IP by multiplexing connections using port numbers?

• A. PAT
• B. NAT
• C. VPN
• D. DHCP

Answer: (A)

Port-based multiplexing lets many internal devices use one public IP by distinguishing each connection with a unique port number. When an inside host starts a connection, the gateway rewrites the source to the single public IP and assigns a new outside port, keeping a table that maps that public port back to the internal host and its original port. The response from the outside world returns to the public IP and that port, and the gateway uses the mapping to forward the data to the correct internal device. This is how multiple internal hosts can share a single public address at the same time. VPNs and DHCP don’t provide this multiplexing function, and basic NAT without port-level multiplexing wouldn’t support many internal hosts on one public IP.