D-Link DFL-2500 User Guide - Page 134

14.2. Address Translation 115 source port to a free port, usually one above 32768, 32789 is used here. The packet is then sent to its destination. The recipient server regards the firewall NATed address as the origin of the packet, processes the packet, and sends its response back to the NATed address. The firewall receives the packet and compares it to its list of open connections. Once it finds the connection in question, it restores the original address and forwards the packet to the real sender. Static Address Translation (SAT) SAT is a type of address translation in which a public IP address is statically mapped to a private IP address. Dynamic NAT is normally used for outgoing traffic, while SAT is used for incoming traffic. For example, using SAT allows an internal host, such as a Web server, to have an unregistered (private) IP address and still be reachable over the Internet. The private IP address of the server is mapped to a public static IP address, which can be seen from the Internet. In D-Link firewalls, SAT is implemented to provide many important functions, for example: - DMZ & Port Forwarding: SAT supports the use of DMZ network to provide pubic services to the Internet, meanwhile protecting the private network from unnecessary disclosure to the outside world. (see 16, DMZ & Port Forwarding) - Server Load Balancing: SAT can redirect connections pointed at some server to randomly selected servers. (see 24, Server Load Balancing) D-Link Firewalls User's Guide