I've recently ditched my cable company and have switched to FiOS. The initial swap went well, unplug from the cable modem and plug into the ONT and things just worked. However, every few hours my IPv6 connections would drop, this is both on my OG Google WiFi and my new Nest WiFi Pro. Here's what I've observed:
FiOS in NYC hands out an /56, Spectrum (cable) hands out a /64 - this is the primary difference that I can see.
The v6 address my clients receive is a /64.
When my connection drops, my Dynamic DNS script (via Cloudflare APIs) reports a new address in a new /64 but the same /56.
I believe that when the lease is renewed by the router a valid IP address in the /56 is offered with a random /64 prefix. This triggers the client to notice that they're not in the same /64 and destroy the previous address.
It seems like an easy solution is for the Google router to treat a /56 as a /64 and use a fixed (or configurable) pad to the /56 prefix. This would ensure that only addresses from a single /64 would be usable - once I have more than 2^64 devices that may be a problem but hopefully that won't be for a while...
Alternatively, changing the client prefix to a /56 may work, but I don't know if this will cause client-side limitations that assume a /64.
An alternative solution that could work for me is to expand the Google One VPN to the Nest WiFi product lines, passing on the IPv6 pinhole configuration from the Nest WiFi. This seems like a lot more work, but adds value to both product lines and expands the greater IPv6 footprint (it took me a while to figure out why my Pixel kept working on IPv6 even with it disabled on the router).
Temporarily (?) I've installed the carrier provided router to fix this issue, but I'd much prefer to switch back to a solution I could manage from the Home app. I have submitted a report via the Home app just after a prefix change occurred in hopes that it helps validate things on Google's end. Please let me know if I can provide any additional information!
