What is diffrence between dynamic NAT and Dynamic policy NAT

Static NAT: Maps an unregistered IP address to a registered IP address on a one-to-one basis. Particularly useful when a device needs to be accessible from outside the network. Dynamic NAT: Maps an unregistered IP address to a registered IP address from a group of registered IP addresses. Dynamic NAT also establishes a one-to-one mapping between unregistered and registered IP address, but the mapping could vary depending on the registered address available in the pool, at the time of communication.

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