Oooh. Ok, I guess it's time to add a router to the closet shelf....
I had the enclosure connected to the time capsule (a router, right?), but it would not stay connected. I have a Gigabit ethernet switch, and I'll try that tonight.
Incidentally, I got the mac mini to recognize the DNS 321 temporarily by configuring the ethernet port to 192.168.0.39 (DHCP, assigned IP), where .39 was made-up to differentiate it from the default address of the DNS-321, 192.168.0.32. This is still working, and the ethernet cable is communicating with the DNS 321, in that, I'm able to configure the device with the web-based GUI at http://192.168.0.32. I'm not able to connect to the server, however, by smb or afp, after an initial time period of being able to do so. The server just fell off of the finder window, and I've been unable to connect to it since then.
Thanks for taking an interest in my case.
5/8/11: more info on above: I used the GUI through the web server to turn the IP address to static, non-DHCP (192.168.0.32). It now comes up reliably. I also read about adding the network drive to the user account through the system preferences window, as "login items." Just drag and drop the network drive. I believe this is the equivalent of "mapping" a Windows drive.