Twice Dynamic NAT Overview
Twice dynamic NAT translates both the source and destination IP addresses. Port mapping is not performed.
The private source address is translated by dynamically assigning a public address from a pool, and the mapping from the original source address to the translated source address is maintained as long as there is at least one active flow that uses this mapping.
The destination address is translated to the IPv4 address of a private server. This redirects traffic destined to a virtual host (identified by the original destination IP address) to the real host (identified by the translated destination IP address). The destination addresses is translated with a one-to-one static mapping to an address in a pool.
Benefits
Allows hosts in the private network to connect with the external domain, while hiding the private network.
Allows a few public IP addresses to be used by several private hosts
Allows external traffic to communicate with a private host without revealing the host’s private IP address
Does not require port mapping