I finally decided to learn IPv6 and deploy it on my home network this year, and the lack of stability in the prefix I get from my ISP has been by far the biggest letdown. It basically neuters the whole “you don’t need NAT any more!” dream of IPv6.
I’ve taken to having both a ULA prefix and a public prefix for hosts in my subnet, but the public one is basically worthless because it changes seemingly every week. I had to put a ton of effort into making a templated pf.conf updated by a dhcpcd hook so that my firewall rules update automatically, but it’s still a shitshow. When my prefix changes, my router doesn’t seem to want to rescind the old RA’s so now I have two public prefixes floating around and half my hosts can’t get to the Internet any more. I had to drop the lifetime to <1hr to mitigate it but it’s a complete joke. If ipv4 fallback didn’t work I’d have a broken network every week.
At this point I’m considering just using NPTv6 and dropping the concept of routable IP’s for my internal hosts altogether. It’s just not worth it. At which point, it’s a stretch to even say IPv6 is worth it.
Sure, I absolutely agree, Comcast deserves to be named and shamed here. But “not worth it” to me doesn’t mean I’m making a judgment against IPv6 as a protocol suite, just that, in practice Comcast’s shitbaggery makes the whole effort hard to justify.
They can give you a static IPv6 prefix, too. But you have to pay extra for a static IPv4 address to get it (which makes what kind of sense?) and you must rent their equipment (ie their router, not just a modem) to get it. So that’s easily $30-$40 more a month (equipment rental plus static IP charge) they’re holding your network hostage for. Pay up or get re-prefixed every week.
It really makes me want to puke that they’re literally incentivized to fuck up my network to try and make the extra upcharge seem worth it. There’s no reason whatsoever they couldn’t just give me the same prefix forever. There’s no shortage of IPv6 space. If I had literally any other choice in ISP I’d drop them in a heartbeat. They should all be thrown in jail.
Somewhere out there there’s a Comcast engineer whose management told them to intentionally configure their DHCP6-PD server to forget (and likely intentionally shuffle) delegations, to pressure customers into ponying up for a static IP. Maybe you’re reading this post some time in the future. I hate you and I wonder how you sleep at night.
I've had the same IPv6 prefix (/60) from Comcast for over 2 years now. I set up my DHCPv6 client with a stable GUID and even after my equipment being off for a couple of days I still pulled the exact same prefix delegation to my CPE.
In my old house where I lived for ~9 years, I had the same IPv6 prefix (/60) from Comcast for a little over 5 years since I turned on IPv6 in 2015 and had not changed until I moved to SF.
Sounds like there's something wrong with your CPE where it is not sending the same GUID to the DHCPv6 server and thus is getting a new prefix delegation each time.
For the first few weeks using IPv6 I used a UniFi security gateway with some pretty standard config (you don’t get to adjust your DUID or anything) and a Comcast business gateway as my modem (it’s also a router, so if there’s a DUID misconfiguration it’s Comcast’s fault). So the Comcast gateway got a /56 and further delegated a /60 to my USG (the Comcast modem has no bridge mode, this is how it has to work), and my prefix still changed 3 or 4 times.
I’ve since changed to my own modem and my own OpenBSD box with a statically configured DUID (randomly generated UUID persisted via the config file) in my dhcpcd.conf. My prefix still changed a few times.
I’ve heard a lot of people saying their prefix has been mostly stable, but it hasn’t been the case for me. Maybe my account is misconfigured on Comcast’s end, maybe something else on their end is wrong, but I’ve checked everything and it looks right on my end.
(My IPv4 address has remained perfectly stable this whole time too. Only my IPv6 prefix seems to be constantly changing. It’s the exactly the opposite of what I’d want, I could care less if my IPv4 address changes, I only need my IPv6 prefix to be stable.)
I’ve taken to having both a ULA prefix and a public prefix for hosts in my subnet, but the public one is basically worthless because it changes seemingly every week. I had to put a ton of effort into making a templated pf.conf updated by a dhcpcd hook so that my firewall rules update automatically, but it’s still a shitshow. When my prefix changes, my router doesn’t seem to want to rescind the old RA’s so now I have two public prefixes floating around and half my hosts can’t get to the Internet any more. I had to drop the lifetime to <1hr to mitigate it but it’s a complete joke. If ipv4 fallback didn’t work I’d have a broken network every week.
At this point I’m considering just using NPTv6 and dropping the concept of routable IP’s for my internal hosts altogether. It’s just not worth it. At which point, it’s a stretch to even say IPv6 is worth it.