Well, delegated IPv6 prefixes are supposed[1] to be static or somewhat persistent, but some ISPs do this, yes. This is most likely a practice carried over from

Well, delegated IPv6 prefixes are supposed[1] to be static or somewhat persistent, but some ISPs do this, yes. This is most likely a practice carried over from IPv4 where there is a small pool of addresses. Fortunately in my experience it's not too common: most ISPs that deployed IPv6 did it the right way. Anyway, to get persistent addresses you can set up a ULA prefix (the equivalent of RFC 1918 addresses) and a simple prefix translation[3]. This is a form of NAT, but unlike the usual IPv4 NAT (actually NAPT) it doesn't deal with ports, so it's slightly less annoying problematic. There also are a few more techniques, like using mDNS and writing firewall rules that match the suffix of the client addresses, but not many CPE allows for this. [1]: https://www.ripe.net/publications/docs/ripe-690/#53-why-persistent-prefix-assignments-are-recommended https://www.ripe.net/publications/docs/ripe-690/#53-why-pers... [2]: https://en.wikipedia.org/wiki/Unique_local_address https://en.wikipedia.org/wiki/Unique_local_address [3]: https://openwrt.org/docs/guide-user/network/ipv6/ipv6.nat6 https://openwrt.org/docs/guide-user/network/ipv6/ipv6.nat6