D-Link NetDefend DFL-210 User Manual page 315

Network security firewall ver 2.26.01

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7.4.7. SAT and FwdFast Rules

We will now try moving the NAT rule between the SAT and FwdFast rules:

What happens now?

External traffic to wan_ip:80 will match rules 1 and 4, and will be sent to wwwsrv. Correct.

Return traffic from wwwsrv:80 will match rules 2 and 3. The replies will therefore be

dynamically address translated. This changes the source port to a completely different port,

which will not work.

The problem can be solved using the following rule set:

External traffic to wan_ip:80 will match rules 1 and 5 and will be sent to wwwsrv.

Return traffic from wwwsrv:80 will match rules 2 and 3.

Internal traffic to wan_ip:80 will match rules 1 and 4, and will be sent to wwwsrv. The sender

address will be the NetDefend Firewall's internal IP address, guaranteeing that return traffic

passes through the NetDefend Firewall.

Return traffic will automatically be handled by the NetDefend Firewall's stateful inspection

Chapter 7. Address Translation

http SETDEST wwwsrv 80

80 -> All SETSRC wan_ip 80

http SETDEST wwwsrv 80

80 -> All SETSRC wan_ip 80

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