What is Port Address Translation (PAT) and how does it differ from Static NAT?

• A. PAT uses a single public IP with different port mappings to multiple private addresses; Static NAT maps each private IP to a distinct public IP 1:1.
• B. PAT maps each private IP to a distinct public IP 1:1; Static NAT uses a single public IP with port translations.
• C. PAT maps private addresses to private addresses only; Static NAT translates to public addresses.
• D. PAT does not use ports; Static NAT uses port translation.

Answer: (B)

Port Address Translation (PAT), often called NAT overload, lets many private hosts share a single public IP by using different port numbers for each connection. When a private device talks to the Internet, the router translates the source address to the single public IP and assigns a unique source port for that conversation. A translation table keeps track of which private host and port map to which public port, so responses are correctly forwarded back.

Static NAT, in contrast, maps each private IP to a specific public IP, 1:1. Each internal device gets its own public address, so no port multiplexing is needed. This requires as many public IPs as there are internal hosts and makes connections straightforward, but uses more public address space.

So PAT is best described as using a single public IP with port mappings to multiple private addresses, while Static NAT provides a direct 1:1 private-to-public mapping.