Firewall Features
The 4300 has a pretty complete set of controls for its NAT + SPI firewall. But since nomenclature has been changed to reflect the product's gaming focus, you may find yourself hunting around a bit to find what you need. You get three ways to forward ports through the 4300's firewall - Virtual Servers (single ports), Special Applications (triggered ports) and Gaming (non-triggered port ranges). Note that for each rule in all three port-forwarding methods you can select from one of 20 day / time schedules that you define.
Figure 5: Virtual Server setup
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Figures 5 and 6 show the built-in application pick lists for the Virtual Server and Special Applications and also that you can add your own applications as well as edit, delete or temporarily disable rules that you define.
Figure 6: Special Applications setup
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Figure 7 shows the Gaming rule setup with part of the rather extensive built-in application pick list, which also includes some non-gaming applications such as BitTorrent (shown).
Figure 7: Gaming rule setup
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The 4300 also provides one more way to allow traffic in through its firewall. The Inbound Filter feature is essentially the same as the Gaming (static port-range forwarding) control, except it allows the port forwarding rule to be restricted to a specific IP or range of IP addresses. And last, but not least, the router has a DMZ function that allows opening all ports to a LAN client of your choice.
With all this port-forwarding flexibility, I thought it odd that the 4300 didn't support UPnP and its NAT Traversal feature. But D-Link told me that UPnP is on the list to be added at some point via a firmware release.