Which form of NAT maps multiple private IP addresses to a single registered IP address by using different ports?

Static NAT creates a permanent one-to-one mapping between a single inside local address and a single inside global address and does not use port multiplexing.

Dynamic NAT maps inside local addresses to addresses drawn from a pool of registered IP addresses, still maintaining a one-to-one ratio per active session without port-based multiplexing.

NAT overloading, also known as Port Address Translation (PAT), allows multiple internal hosts to share a single registered IP address simultaneously. Each translation entry is uniquely identified by the combination of the inside local IP address, inside global IP address, and a dynamically assigned source port number, enabling the router to correctly demultiplex return traffic.

Overlapping NAT is used when the inside and outside networks use the same IP address space, requiring translation on both sides, and is unrelated to port-based multiplexing.

'Port loading' is not a standard Cisco NAT term; the correct term for this functionality is overloading or PAT.