Snuffy
Based on your posts, I would have to describe you as what I percieve as the typical user struggling to get ftp up on one of these units - I could be wrong, it's just my perception.
I would guess that you have limited networking experience, and this might be your first foray into any sort of server hosting and port forwarding. Am I close?
You seem to be at the point that would be described as having just enough knowledge to be dangerous, and not enough to know what you're really about.
Before your edit, your post mentioned dynamic DNS and the DNS-321's DNS settings, by which I assume you refer to the DNS server entries in the LAN settings page. Now you're talking about getting an ip address from ipconfig.
Well - it just doesn't work that way - why not try running ipconfig and see how the ip address compares to the one you actually used.
A couple of quick points ...
First - ip addressing - if your computer is behind a router, when you run ipconfig, you'll get what is called a private ip address, one from three possible ranges, set aside for private use - these are sometimes (incorrectly) called non-routable addresses - they are routable, but because theyare reserved for private use, most ISP's will drop them at their ingress/egress routers.
The ip address you need is the public ip address that your ISP uses to identify your router.
In most cases, the ISP will provide a dynamic address, one that changes from time to time, static addresses may be available, but usually cost a bit more - the problem that this creates when hosting a server is that you, more often than not, don't know when it changes, don't know what it was changed to, and have no way to find out if you're not on the network - this is why dynamic DNS is used.
You register a name with the dynamic DNS service, and you configure a dynamic DNS client that runs on a device on your network to periodically check for changes in the ip address and report these changes to the dynamic DNS servers, so that you can, through the use of the name you registered, determine the public ip address of your router, and so make a connection to it.
Second - DNS settings - the DNS server settings on the DNS-321's LAN settings page bear only a passing resemblance to the dynamic DNS services, and there is nothing that you can enter there to help locate your router on the internet - these settings are actually used, so to speak, for a diametrically opposed purpose - they tell the DNS-321 where to find a server that will allow it to resolve names you may have entered (email servers, time servers) to actual ip addresses.
Back to my perception - what a lot of the newcomers are looking for is instant gratification - a "how to" that will guide them step by step through the process, without them having to learn the basics, which is just not possible, given the variations mentioned in my earlier post.
Let's compare this to driving a car - the basic controls (accelerator, brake, steering, etc.) on a car don't change from one car to the next - consider this the user interface - but, what is under the hood does, so even though, most people can drive a car, if they're going to do their own maintenance, it calls for a lot more learning.
Networks are very much similar - from a user point of view - they don't change much, you can get on your PC and browse the net, download stuff - but - when you want to get under the hood of your network, a lot more learning is also required.
Like maintaining your car - you can learn to do it yourself, or you can pay someone else to do it - but there is no easy step-by-step guide.
Now - if you want to learn how it works (as compared to trying this and trying that and getting frustrated along the way, as I have seen many users do), get yourself some tutorials and start reading - I've already listed the areas that need to be covered.