Basic NAT and PAT
Two kinds of network address translation exist:
* PAT (Port Address Translation) - The type popularly, but incorrectly, called simply “NAT” (also sometimes named “Network Address Port Translation, NAPT”) refers to network address translation involving the mapping of port numbers, allowing multiple machines to share a single IP address.
* Basic NAT - The other, technically simpler, forms—”one-to-one NAT”, “basic NAT”, “static NAT” and “pooled NAT”—involve only address translation, not port mapping. This requires an external IP address for each simultaneous connection. Broadband routers often use this feature, sometimes labelled “DMZ host”, to allow a designated computer to accept all external connections even when the router itself uses the only available external IP address.
NAT with port-translation (i.e. PAT) comes in two sub-types: source address translation (source NAT), which re-writes the IP address of the computer which initiated the connection; and its counterpart, destination address translation (destination NAT). In practice, both are usually used together in coordination for two-way communication.