So I don’t have the changing ip issue. I do however have an issue if I want to change ISP as it’s a whole mess of rules to update rather than a couple of dns entries and two dst nat rule (one per public IP)
I believe the idea in v6 if you have multiple prefixes on the same network - including a local fc00::/7 one for local services. Layers and layers of things to break.
Using Openwrt which pretty much all home routers are built on, all I have to do is tell my router which offset to give my subnets from the prefix and it does the rest.
Both for subdividing up the prefix from the ISP and my ULA prefix I use for internal devices.
I have changed ISPs I think 3 times with no ill effects. Plus it works when my ISP occasionally gives me a new prefix.
The only tweaking I had to do was when I went from an ISP that game me a /48 to one that only gave me a /56. I had been greedy and was handing a /56 to my internal router. I changed that to a /60 and updates it's expectations about which subnets it could hand out and all was good.
But I expect two layers of home routers without NAT is a bit of an exception.
IPv6 also has local addresses, but a lot more of them. Anything starting with fd00::/8 is a local address with 40 bits available as the network number. So you can set up your local network with the prefix fdXX:XXXX:XXXX::/48 (where the Xs are chosen randomly) as the prefix and still have 16 bits left over for different subnets if you want. These addresses do not change when your ISP changes your public prefix.
And if you want to add reverse dns for SLAAC addresses then just have your router listen for ICMPv6 Neighbor Announcement addresses and use them to update your DNS server as appropriate. Or configure your servers to use stable addresses based on their MAC address rather than random addresses (which are better for privacy), and then just configure the DNS as you add and remove servers.
This conversation is going in circles.
(same for ping)
Yes, a topic of active discussion at the IETF. See perhaps BCP RFC 9096, "Improving the Reaction of Customer Edge Routers to IPv6 Renumbering Events":
* https://datatracker.ietf.org/doc/html/rfc9096
And informational RFC 8978, "Reaction of IPv6 Stateless Address Autoconfiguration (SLAAC) to Flash-Renumbering Events":
* https://datatracker.ietf.org/doc/html/rfc8978
A few drafts, like "Improving the Robustness of Stateless Address Autoconfiguration (SLAAC) to Flash Renumbering Events":
* https://datatracker.ietf.org/doc/html/draft-ietf-6man-slaac-...
Using ULA seems to be what a lot of folks recommend:
Unlike IPv4, my LAN addresses include the prefix, so every time they change it, all my LAN addresses change.
Combined with the lack of DHCP6 support in many devices, this means reverse DNS lookups from IP to hostname can't be done, making identifying devices by their IP essentially impossible.