How does NAT translate internal private addresses to public addresses?

• A. NAT maps private addresses to public addresses (or ranges) as packets pass through the router.
• B. NAT maps public addresses to private addresses.
• C. NAT removes all address translation.
• D. NAT uses the same public address for every host.

Answer: (A)

NAT works by translating private internal addresses into public addresses as traffic leaves the network through the NAT device (usually a router). When an internal host sends a packet, the router replaces the private source IP with a public IP from a pool (or with a single public IP when using Port Address Translation) and may alter the source port as well. It keeps a mapping of these translations so that when the reply returns, the router can translate the destination back to the correct private address and forward the packet inside the local network. This process lets many private devices share public addresses and reach external networks.

The other ideas don’t fit as well: NAT is about private-to-public translation for outbound traffic, not typically a reversal of that direction; it doesn’t eliminate translation entirely; and while a single public IP can be used in PAT, NAT isn’t inherently limited to always using the same public address for every host.