IPv4 and IPv6 addresses are reachable from all computers on the LAN.
Actual Behaviour:
IPv4 addresses return Destination host unreachable from any machine except the Pi-hole. Names that resolve to IPv6 addresses seem to be reachable from anywhere.
My BT Smart Hub 2 doesn't allow me to specify a DNS server, so I have disabled its DHCP service and I am using Pi-hole for DHCP. On the pi I can ping both IPv6 and IPv4 addresses and access their web sites. But other machines on the LAN can only reach IPv6 addresses.
ping google.com
Pinging google.com [2607:f8b0:4002:c00::64] with 32 bytes of data:
Reply from 2607:f8b0:4002:c00::64: time=97ms
ping pi-hole.net
Pinging pi-hole.net [192.124.249.118] with 32 bytes of data:
Reply from 192.168.1.171: Destination host unreachable.
tracert pi-hole.net
Tracing route to pi-hole.net [192.124.249.118]
over a maximum of 30 hops
1 DESK01.lan [192.168.1.171] reports: Destination host unreachable.
Clients most likely will get DNS servers assigned via IPv6 router discovery which are not Pi-holed.
Try figure out a way to disable IPv6 entirely on the router for the LAN side.
You most likely dont need/want a dual stack and it only complicates matters.
For any DHCP change you make, you have to let the client devices renew their DHCP leases for the changes to become effective.
Usually dis and reconnecting them from/to network does that.
Or reboot your client devices.
In general, ping is not a good choice for analysing DNS issues.
In your case, it actually shows that name resolution succeeded (pi-hole.net is[192.124.249.118]) and indicates a networking problem.
Is 192.168.1.171 the IP of the client you've run the ping from?
Then the ping would have never left that client, likely because it doesn't know a gateway to send it to. What's your router's IP address?