Static PD and DHCP6 DUID on 2.4.4
I have business service from Mediacom with a /30 static IPv4 block. They've supported IPv6 for a while now. The WAN interface in pfSense has been set to a DHCPv6 Prefix Delegation size of 64, and the LAN interface is set to track the WAN interface for IPv6. This configuration was working great for several months, even after rebooting pfSense a few times.
This morning when I upgraded pfSense from 2.4.3 to 2.4.4, Mediacom issued a different /64 for the LAN. While tracking down the issue, I noticed that under System / Advanced / Networking, the DHCP6 DUID had not been set. I set it to DUID-LLT. The /64 on the LAN hasn't changed across a small number of reboots so far today.
Is this DHCP6 DUID setting likely the reason the LAN was issued a different /64 after the upgrade? If I call up Mediacom Business Support to ask specifically about a static /64 assignment, will they need me to set something else in pfSense to make the /64 assignment stick? I know these are probably questions for Mediacom, but I don't like asking them anything without having a pretty good idea of the right answer first. Thanks.
The DUID can change for a number of reasons, which is why we added the box to set it static. The DUID is probably what they key static assignments off of, so that's not too surprising to see.
So what you probably need to do is see what the DUID is now and then set it to that explicitly, then it won't change again.