D-Link DFL-800-AV-12 User Manual - Page 205
Dynamic Network Address, Translation, Example 7.1. Adding a NAT rule
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7.1. Dynamic Network Address Translation Chapter 7. Address Translation Publish entry configured for the egress interface. Otherwise, the return traffic will not be received by the D-Link Firewall. The following example illustrates how NAT is applied in practice on a new connection: 1. The sender, for example 192.168.1.5, sends a packet from a dynamically assigned port, for instance, port 1038, to a server, for example 195.55.66.77 port 80. 192.168.1.5:1038 => 195.55.66.77:80 2. In this example, the Use Interface Address option is used, and we will use 195.11.22.33 as the interface address. In addition, the source port is changed to a free port on the D-Link Firewall, usually one above 32768. In this example, we will use port 32789. The packet is then sent to its destination. 195.11.22.33:32789 => 195.55.66.77:80 3. The recipient server then processes the packet and sends its response. 195.55.66.77:80 => 195.11.22.33:32789 4. NetDefendOS 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. 195.55.66.77:80 => 192.168.1.5:1038 5. The original sender receives the response. Example 7.1. Adding a NAT rule To add a NAT rule that will perform address translation for all HTTP traffic originating from the internal network, follow the steps outlined below: CLI gw-world:/> add IPRule Action=NAT Service=http SourceInterface=lan SourceNetwork=lannet DestinationInterface=any DestinationNetwork=all-nets Name=NAT_HTTP NATAction=UseInterfaceAddress Web Interface 1. Go to Rules > IP Rules > Add > IPRule 2. Specify a suitable name for the rule, eg. NAT_HTTP 3. Now enter: • Action: NAT • Service: http • Source Interface: lan • Source Network: lannet • Destination Interface: any • Destination Network: all-nets 4. Under the NAT tab, make sure that the Use Interface Address option is selected 5. Click OK 205