D-Link 800 - DFL 800 - Security Appliance, User Manual, Page: 285 / 469

many NAT pools and a single pool can be used in more than one NAT rule. This topic is
discussed further in Section 7.2, “NAT Pools”.
Applying NAT Translation
The following 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 now 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
First, change the current category to be the main IP rule set:
gw-world:/> cc IPRuleSet main
Now, create the IP rule:
gw-world:/main> add IPRule Action=NAT Service=http SourceInterface=lan
SourceNetwork=lannet DestinationInterface=any
DestinationNetwork=all-nets Name=NAT_HTTP NATAction=UseInterfaceAddress
Return to the top level:
gw-world:/main> cc
Web Interface
1. Go to Rules > IP Rules > Add > IPRule
7.1. NAT Chapter 7. Address Translation
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