All of a sudden, PiHole stopped working and says that it "lost connection to API". The backup microSD card gave the same problem. Turning off the pihole DHCP server seems to allow FTL to work but only for localhost as it doesn't answer queries from any other LAN clients. I have had to revert to using the router as the DHCP server and have had to bypass PiHole as DNS as PiHole is not responding to anything but localhost (as I said).
*** [ DIAGNOSING ]: Networking
[✗] No IPv6 address(es) found on the eth0 interface.
*** [ DIAGNOSING ]: Name resolution (IPv6) using a random blocked domain and a known ad-serving domain
[✗] Failed to resolve emaildgqw.com via localhost (::1)
[✗] Failed to resolve emaildgqw.com via Pi-hole (2403:5800:7101:f00:efa0:15e8:5e6d:75c3)
[✗] Failed to resolve doubleclick.com via a remote, public DNS server (2001:4860:4860::8888)
If I remember some of your previous posts correctly, you set up a static IPv6 address in your Pi-hole's dhcpcd.conf.
So if your ISP would have changed your IPv6 prefix, that wouldn't propagate to your Pi-hole.
Verify your static IP assignment still matches your current IPv6 prefix as distributed by your router.
My IPv6 prefix has not changed as it's permanent. I can now get LAN clients to access the PiHole for DNS, I had changed the interface listening behaviour in an effort to get this to work. But it does seem that IPv6 is down in my network. I'll reboot the router and see.
dhcpcd.conf is ok, however, running ifconfig does not show an IPv6 address for the eth0 interface. Would you know why that is? All my other LAN devices are getting IPv6 addresses.
I trust you already checked the usual suspects, any new software on the Pi-hole, new firewall rules (blocking ICMPv6 perhaps?), or rebooting your Pi-hole?
Yeah, rebooting doesn't seem to give the Rpi its IPv6 address back. I wonder what happened? Could it be anything to do with the pihole -r command that I used?
Try if manually adding an IPv6 address would work for you:
ip address add 2403:5800:xxxxxxxx/64 dev eth0
EDIT: I'm not certain your final domain_search= line is a valid option, it doesn't show up in the man pages for dhcpcd.conf. Try commenting it out and restart.
I'll be offline in a minute, so may not be able to stay involved.
The issue seems to be that the Rpi4 is no longer getting IPv6 connectivity but everything else in my LAN does. Does anyone know how to re-enable IPv6 working on the Rpi4?