Pi-hole 5.0 fails to create ipv6 ranges for DHCP

[Bucking_Horn]

@michi_e

As mentioned in my first post, when a client requests DHCPv6, the only message in the log is:

dnsmasq-dhcp[2738]: no address range available for DHCPv6 request via eth0

There should be some RTR-SOLICIT and RTR-ADVERT messages, at least for your fd00:: prefix.

@doncarajo

I had the same problem and it was fixed by putting the public IPv6 address after "static ip6_address=" in dhcpcd.conf with the /64 after it.

Thanks, doncarajo - we've already checked prefix length for static IPs earlier.

michi_e, your dhcpcd.conf as posted above looks inconspicious to me. It shows you are not using public IPv6 addresses and you correctly attach prefixes to IPv6 addresses as well.

However, I noticed you instruct dhcpcd to generate a DUID.
This is perfectly valid, so the following may be a bit of a far call:
duid may only ever cause trouble if you happened to run an additional machine from the same image in the same network, as that DUID gets stored in /etc/dhcpcd.duid, but needs to be unique within your network.
If you do not run such a second machine, this would not be related to your issue at all.

@michi_e

First, I installed dnsmasq via apt and saw DHCPv6 work—but this was version 2.8, which also had no problems in previous Pi-hole. So I tried with the current version of dnsmasq (2.81) which also works.

This seems to imply that somehow the new dnsmasq version of Pi-hole 5 is involved.

I have tested both Pi-hole v4 and 5.0 when investigating doncarajo's issue (where this suspicion also arose, but wasn't confirmed) - it might be worth to read my analysis results in that post.
While I was able to provoke the same "no address range available" message by disabling distribution of a ULA prefix, I could not reproduce the error itself (at least not until the prefix length root cause was identified later).