Address Assignment Methods

NAT uses one of two methods to assign a translated IP address: static translation or dynamic translation.

Static Translations

You enter static translations as direct configuration settings that remain in the translation table until you remove them. You use static translations when you must initiate connections from both the inside and outside interfaces, or when the translation is not subject to change.

Dynamic Translations

Dynamic translations use access list rules, to determine whether to apply NAT to incoming traffic, and NAT address pools, from which a NAT translation can obtain IP addresses. You use dynamic translation when you want the NAT router to initiate and manage address translation and session flows between address realms on demand.