Destination NAT Overview

Destination NAT translates the destination addresses and ports of packets.

Destination NAT translates public IP addresses into private IP addresses so that users on the Internet can use public IP addresses to access a server on the intranet. Figure 1 shows the translation process.

Figure 1 Mechanism of destination NAT

When an extranet user accesses the intranet server, the FW performs as follows:

1. Upon receiving the packets destined from the extranet user to the intranet server, the FW translates the public destination addresses into private destination addresses.
2. Upon receiving the return packets, the FW translates the private source addresses back to public source addresses.

Based on whether post-NAT destination addresses are fixed, destination NAT falls into static destination NAT and dynamic destination NAT.