Showing local hostnames instead of IPv6 hostnames on Top Clients lists

[fyreous]

Expected Behaviour:

Running PiHole v6 on my network and I have conditional forwarding configured properly (or so I think) for both my IPv4 and IPv6 subnets and gateway. My gateway is the DHCP server and assigns local DNS hostnames to all my clients. Example conditional forwarding config:

true,192.168.0.0/23,192.168.0.1,home.arpa
true,2601:6012:8655:aa32::/64,2601:6012:8655:aa32::1,home.arpa

The goal is that for devices in my local subnet, whether IPv4 or IPv6, I see the local hostnames assigned (e.g., sam-iphone.home.arpa).

Actual Behaviour:

Instead, what I see is the IPv6 hostname assigned by my ISP to every device. For example, "syn-2601-6012-8655-aa32-c378-15ad-4587-e821.res6.spectrum.com".

However, I know that PiHole "sees" or knows the local hostname of the device as well, because when I go to the "Tools > Network" page of the web interface, I can see all the dynamic IPv6 hostnames, plus the local hostname, all mapped back to the device's MAC address.

This tells me that PiHole can definitely see all the hostnames (including the local hostname) associated to a given MAC address, but the Top Clients list is just choosing to display one of the dynamic IPv6 hostnames from my ISP to that device, instead of the local one.

Is there a way to adjust this behavior?

[Bucking_Horn]

Your observation is expected:
DNS resolution for public IPv6 GUAs (range 2000::/3) is public, i.e. your router isn't authoritative for those reverse lookups - your ISP is.

Commonly, your ISP would run authoritative DNS servers responsible for reverse resolution of IPv6 addresses issued by it.
ISPs may configure their DNS servers to answer reverse lookups with NODATA or NXDOMAIN, or they may return a generic domain, synthesised by using IPv6 address information along with your ISP's TLD.

You could consider to use IPv6 ULAs for local communication, provided your router supports it, and adjust IPv6 DNS server addresses as advertised by your router accordingly, as well as your Pi-hole's Conditional Forwarding.

Alternatively, you could configure your router to NOT advertise or offer an IPv6 DNS resolver address in your home network (not all routers would support this). That way, clients will talk to your Pi-hole strictly via IPv4, making it a lot easier to associate them with hostnames.

[fyreous]

Appreciate the explanation, thanks. Switching to ULA's did the trick for me!