Dear gurus and wizards of the sacred DNS,
Please help me, a lonely newcommer, with this trivial, yet pressing matter!
(This IS a rather lengthy rant, so if you choose to read it; you might want to fill up your cup with coffee, tea or other favourite beverage)
I've searched high and low across the wide web, but I have found no real answer to this problem;
Recently, I bought the DIR-655 because the gods of thunder decided to euthanize my old WAP. The original plan was to mate this up with a Tilgin VOOD-modem (modem and router in one; a heap of scrap in my uneducated eyes) in order to make networking within my appartment somewhat easier.
Got it safely indoors, plugged it in as the manual told me, and got it going (my old WAP was also a D-LINK, so the interface was somewhat familiar). Checked cabled connection, worked fine, and I got the wireless-bit to function as well. But then I, or my Xbox 360 to be right on the money, encountered a little problem. As I understand from a little bit of research, I found out that this was a dreaded phenomenon known as
"Moderate NAT"
Before I got the old WAP indoors, I used the onboard router in the TILGIN to do the switching. I used to have this problem back then also, but solved it by opening some of the ports on the modem. Then it switched to "Open NAT", and worked like a charm. Now however, I have ran into a problem I can't dig myself out of. I have tried DMZ, opening numerous ports all the way to the full monty, but I can’t get that NAT to wander into the more acceptable range. And then it became clear that the internet on my laptop was somewhat amputated as well; simple youtube-videos became harder to load (sometimes it actually had to stop for extended streaming!), and this is not acceptable on a 20 mbt DSL-line!
More research revealed that a smart idea could be to just bridge the modem, and let the router do what it’s made to do; routing. Today, the WAN-port of the DIR-655 is connected to a LAN-port in the TILGIN. A somewhat boring call to my ISP was made, who could tell me that this modem was not bridgeable (just my luck), but there was a, somewhat crude, makeshift solution; anything connected to the internal IP known as 192.168.1.33 went into DMZ with the modem; no restraints, all ports open. This could, in theory, remove the bottleneck caused by the modem.

But the problems, being much like beers on a Saturday night; they always tend to come in raging hordes, was not over. When I tried to connect to the modem last night, it showed that the DIR-655 was given the IP 192.168.1.4. By now, I have tinkered around enough to know how to reserve the -1.33 IP on the modem for the DIR, but one problem remains;
What do I do to make the DIR accept the -1.33 address, instead of getting a new -1.4? If this was a computer running windows, or even Linux (Mint, I’m not grown up enough to run anything else

), I just had to set the IP for the computer to static with that address. But I have no clue what so ever on how to do this with the DIR, if it’s even possible!
Please, is this something I do on the DIR? Or on the modem? Or both? Or is it just impossible? Or is it me who is just to dumb for this, and should take up something else, like gardening?