Adding A Nat Rule - D-Link NetDefend DFL-210 User Manual

7.1. Dynamic Network Address
Translation
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
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
Publish entry configured for the egress interface. Otherwise, the
return traffic will not be received by the D-Link Firewall.
SourceNetwork=lannet DestinationInterface=any
DestinationNetwork=all-nets Name=NAT_HTTP NATAction=UseInterfaceAddress
205
Chapter 7. Address Translation