I previously had my Windows server, which handles VPN, on a static IP. However, I just moved and I can only get Comcast (CenturyLink doesn't have fiber into our area yet).
And Comcast is all dynamic IP. The Comcast tech claimed that any packet that get to the modem was passed on to the internal subnet and delivered to all devices inside. The Comcast SP-6 modem connects to a dumb switch and all systems, including my Windows server, are connected directly to that switch.
What do I need to do to get this working? And I think this includes mapping the external IP address to the CNAME that I have for my certificate as Windows requires a certificate from a recognized authority.