Which option enables one public address to be used for multiple internal private hosts?
- PAT
- DHCP
- static NAT
- dynamic NAT
Explanation: Port Address Translation (PAT), also referred to as NAT overloading, is the specific implementation of NAT that allows multiple internal private hosts to share a single public (inside global) IPv4 address for external communication. This is a many-to-one mapping process where the router uses unique TCP or UDP port numbers to differentiate between the various internal client sessions.
When a response returns from the internet, the router uses the destination port number to determine which specific internal host should receive the packet, a mechanism known as connection tracking. Because port numbers are 16-bit values, a single public IP address can theoretically support as many as 65,536 internal translations.
In contrast, other NAT types do not support this specific "many-to-one" sharing:
- Static NAT maps a single private address to a single public address (one-to-one).
- Dynamic NAT maps private addresses to a pool of available public addresses rather than a single one.
- DHCP is used for address allocation, not translation.
Related exam: Modules 8 – 13: Checkpoint Exam: Network Routing Answers (CCNP ENCOR v9)
