DNS Priority, IPv4, IPv6

[macklij]

I've just been reading about UniFi access point issues with IPv6 multicast. It's a 3 year old post that pretty much describes the issue. I am trying to find if it was ever resolved.
https://community.ui.com/questions/Bug-IPv6-Multicast-Traffic-is-dropped-by-AccessPoints-on-5GHz-WiFi-Clients-loose-IPv6-address/2541cb8f-efd9-41ed-82bd-42145956fddb?page=1

Also wondering if some of the known issues with Windows 10 IPv6 haven't been solved. I have exactly 'Issue 1' (paragraph 4) of this post https://www.reddit.com/r/ipv6/comments/j9j4j2/windows_10_2004_19041_has_multiple_rdnss_issues/
Interestingly my son has just had this issue on his PC, which is wired, not Wi-Fi.  That may make the whole UniFi thing moot, apart from the iPhone losing DNS IPv6 addresses after a while.

It's very convoluted, and part of me says 'enough': just let DNS servers be contacted on IPv4. It won't stop IPv6 traffic working.

[doktornotor]

No, it's never been solved properly. Multicast is randomly broken with various FW versions both on APs and switches.

[Maurice]

I think the Windows issue you linked to is related to the preference of DHCP over Router Advertisements which I mentioned before. Windows determines the priority of (dynamic) DNS servers based on how they were assigned:

1. DHCPv6
2. DHCPv4
3. Router Advertisements

At least that was the case when I was still using dual-stack (it's been a while). It was a deliberate design choice by Microsoft. The RDNSS option in Router Advertisements is kind of an afterthought and not part of the original ND RFCs, so when Microsoft started supporting this in Windows 10, it was merely intended as a fallback for IPv6-only networks without DHCP.

Just use (stateless) DHCPv6 and you should be good.

[macklij]

Thanks both

Good to know Ubiquiti haven't sorted that yet. I am using one of their PoE switches too, so it’s a double whammy.

There is definitely an MS Windows thing going on too - even with stateless DHCP. The DHCPv6 assigned DNS server addresses don't always appear - and last night found to be on wired (via an unmanaged Netgear switch) as well as wireless.

I may play further during the week.