Just a suggestion.
Break the project into smaller parts and make sure each of the basic blocks works before trying to make the whole thing work.
You can test the DDNS functionality by pinging the URL, even if the ping fails, it should report the ip address it was trying to ping and that should match the WAN address shown in your router's status page or at
http://whatismyipaddress.comIf the URL does not resolve to the correct ip address or is reported as an unknown address, then you need to fix a DDNS problem, if it does resolve correctly then your problem is not DDNS, but either port forwarding or the ftp server itself.
Let's look at the ftp server first - because that is easier and to a certain extent more logical.
First you need to have the DNS-321 at a static ip address or at the very least a reserved DHCP address, and then you need to create an ftp user, assign a share and start the ftp server - once you have done that, test it from the local network, go to any computer, open a command prompt and enter ftp local_ip_of_ DNS-321, you should see a prompt asking you to login - if you don't post with the error message and we'll take it from there - if you do, login with the username and password and do a directory listing (dir) and then disconnect (bye)
By the way - the only reason I'm using the command line ftp client is it gives nice clear error messages - you can also use your internet browser - enter ftp://local_ip_of_DNS_321 - or whatever ftp client you choose.
If you have gotten this far, we can now look at the remote access - first you have to foward the required port (21), to tell the Motorola router that when it gets a request on the port, that it routes that request to the DNS-321 - since I am not familiar with the Motorola products, I'm going to give you a link to
www.portfoward.comAfter you have setup the port forwarding try to connect
from outside your network - if you try to test from inside the same network it may or may not work, depending on whether or not your router supports loopback.
For this test, if you are using the command prompt, enter - ftp your_domain_name.dyndns.org - or - ftp <your_routers_public_ip_address> - and in your browser - ftp://your_domain_name.dyndns.org - or - ftp://<your_routers_public_ip_address>
Please note - the above assumes you are running your ftp server on the standard ftp port 21 - if you plan to use a non-standard port, I would suggest you set it up on port 21 first and verify functionality, as outlined above and then change to a non-standard port. Yes, it does involve more work, and in fact, repeating several steps, but it allows you to pinpoint where the problem lies.