said by Cubbies:The modem doesn't seem to save the settings except from dyn. I really don't want to pay for dyn. How can I get the others to work?
Yep, Dyn stabbed a lot of people in the back when they discontinued their free DDNS service after offering it (and getting router vendors to include it) for so many years. I understand why they did it, but it still sucks.
If you don't want to pay for a Dyn account, you can run a standalone DDNS client from a provider who still offers a free service on a PC device behind your DPC3939.
I run the Namecheap DDNS client on two servers, a PC workstation, and a notebook; and I have no problems keeping them synchronized. I actually use Namecheap as my domain registrar, so I have a paid account with them, but before I switched to their service, I used their FreeDNS service to make sure that it would work. To my knowledge, they still offer the FreeDNS service. If you decide to use Namecheap, and your PC(s) run Windows, use their version 2 beta client, it works much better than their older client. If you run a *nix OS, you can use ddclient or lynx to sync the DDNS service (I use lynx on my Linux server to sync multiple hostnames with a cron script).