If any of this may get back to D-Link, let me be a bit more specific:
Using the 1.02 firmware I had my DSL modem set up in a PPP IP Connect mode, which basically limits the DSL modem to just being a modem; it uses DHCP to pass configuration information to the router (in this case the DGL-4500.) It passes the external WAN IP from my ISP, DNS servers and allows the DGL-4500 to perform NAT and firewall functions, elegantly allowing me to NOT have to worry about port forwarding twice, for example.
When I upgraded to the 1.12 firmware the DGL-4500 would still receive the correct external IP as assigned by my ISP and then delegated via DHCP to the DGL-4500; it would receive correct DNS server information and gateway info also. To all appearances it looked right. But I couldn't access my DSL modem, and couldnt' access the internet. It was like NAT traversal just doesn't function any longer, or something.
I had to enable NAT on my DSL modem (previously unused due to the aforementioned PPP IP Connect bridging-type mode) in order to access anything via the DGL-4500's WAN port. I then put the DGL-4500 in the DMZ of the DSL router to work-around having to port forward twice through the DSL modem through the DGL-4500.
Port forwarding is acting very funny. On some games it works fine still for hosting games (Warcraft 3.) However, Company of Heroes doesn't work at all. CoH developer info says to forward UDP 6112 & 30260; if I do so, I can't access their online matchmaking service Relic Online at all. If I disable the port forward rule I can access Relic Online but can't host games (without port forwarding.) This port forward rule worked in 1.02.
The only thing I can think that is different between Warcraft 3 / Blizzard.net and Company of Heroes / Relic Online is that Relic uses UDP 30260 for outgoing communication and UDP 6112 for incoming, wheras Blizzard.net uses TCP 6112 for both incoming and outgoing (I think.) I tried setting up the Company of Heroes rule for just UDP 6112, but with the same result - no connection to Relic Online at all, like the port was blocked to my computer.
I did have success in setting up a port triggering rule, using UDP 30260 as the trigger to open UDP 6112. What I don't understand is why the port forward rule worked prior to the firmware upgrade and why it doesn't now; and why does it work still with Warcraft 3 and not with Relic Online? I don't know enough about networking to tell you the answer to that one.
My vonage phone worked with the 1.02 firmware without any port forward rules or any special setup. Just plug and play. Now with the 1.12 I was able to receive calls but outgoing communications were either blocked completely or blocked after a few seconds. I could call out, speak for a few seconds, and then lose outgoing voice comms (but be able to hear the other person.) Most of the time I just couldn't call out at all, although I'm still receiving calls, although I would still either be unable to talk or only be able to talk for a few seconds before losing outgoing voice altogether.
Port forward rules based on the Vonage help site (they say a random UDP port 10000 to 20000 is selected for in/out voice communications) blocked my phone from working at all. Port triggering didn't work. Disabling SPI on the firewall finally allowed me to use my phone most of the time, although I still occasionally get some dropped voice comms or can't dial out; I am still receiving calls.
GoToMyPC, a remote PC access service, also ceased to function on the 1.12 firmware (I am using my computer as a client to help my Mom keep her computer updated.) Their help site says port forwarding isn't required, and only list some outbound ports that are required for communication, so I don't see how I can fix that.
For troubleshooting purposes I turned off all software based firewalls to prevent this from being a factor.
DHCP IP Reservation seems to function properly; my first thought was that maybe all these problems are caused by incorrect IP assignments. But everything seems to be assigned the correct IPs.
The DSL modem I am using is Paradyne (now Zhone) 6112-I2 using the latest 03.01.08 firmware (from May 2008 or so.) Again, it worked fine with the 1.02 firmware.