PTR issues with pi-hole 6: Unable to resolve PTR (UDP) and cannot receive UPD DNS reply - timeout

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1

Recently, I’m experiening performance issues with my Pi-hole 6 as well as some PTR warnings/errors.

Expected Behaviour:

Being able to resolve remote, DNCP assigned hostname/IP adresses as well as local DNS hostname/Ip Adresses as well as CNAMET in timely manner.

Operating System Raspian (debian 12)

  • Hardware: Raspberry Pi 5 (4GB)
  • Running natively.

Actual Behaviour:

I’m regularly getting DNS timeout errors and/or DNS probe errors. My Proxmox servers can’t seem to find the NFS share I’ve exposed on my NAS. Also, I’m seeing a bunch of PTR errors that all seems to refer to hosts that are in my local DNS.

2025-10-27 15:00:22.042 ERROR Cannot receive UDP DNS reply: Timeout - no response from upstream DNS server
2025-10-27 15:00:22.042 INFO Tried to resolve PTR "11.0.168.192.in-addr.arpa" on 127.0.0.1#53 (UDP)
2025-10-27 16:00:25.306 ERROR Cannot receive UDP DNS reply: Timeout - no response from upstream DNS server
2025-10-27 16:00:25.306 INFO Tried to resolve PTR "11.0.168.192.in-addr.arpa" on 127.0.0.1#53 (UDP)
2025-10-27 17:00:23.354 ERROR Cannot receive UDP DNS reply: Timeout - no response from upstream DNS server
2025-10-27 17:00:23.354 INFO Tried to resolve PTR "11.0.168.192.in-addr.arpa" on 127.0.0.1#53 (UDP)

Here’s a set of examples from today

2025-10-30 12:32:32.705 INFO Compiled 3 allow and 0 deny regex for 79 clients in 66.6 msec
2025-10-30 13:00:21.114 ERROR Cannot receive UDP DNS reply: Timeout - no response from upstream DNS server
2025-10-30 13:00:21.114 INFO Tried to resolve PTR "7.0.168.192.in-addr.arpa" on 127.0.0.1#53 (UDP)
2025-10-30 14:00:19.290 ERROR Cannot receive UDP DNS reply: Timeout - no response from upstream DNS server
2025-10-30 14:00:19.290 INFO Tried to resolve PTR "7.0.168.192.in-addr.arpa" on 127.0.0.1#53 (UDP)
2025-10-30 15:00:17.498 ERROR Cannot receive UDP DNS reply: Timeout - no response from upstream DNS server
2025-10-30 15:00:17.498 INFO Tried to resolve PTR "7.0.168.192.in-addr.arpa" on 127.0.0.1#53 (UDP)
2025-10-30 16:00:24.858 ERROR Cannot receive UDP DNS reply: Timeout - no response from upstream DNS server
2025-10-30 16:00:24.858 INFO Tried to resolve PTR "7.0.168.192.in-addr.arpa" on 127.0.0.1#53 (UDP)
2025-10-30 18:00:21.466 ERROR Cannot receive UDP DNS reply: Timeout - no response from upstream DNS server
2025-10-30 18:00:21.466 INFO Tried to resolve PTR "7.0.168.192.in-addr.arpa" on 127.0.0.1#53 (UDP)

Debug Token: https://tricorder.pi-hole.net/EA4Hn0hC/

2

I see a number of these entries in my logs too, in my case, and maybe yours too I think it is something to do with pi-hole==>unbound.

Those IPs are internal IPs as you mention, and from what I’ve read so far (but with limited understanding) I understand it to mean unbound cannot resolve those IPs to hostnames because it is a recursive DNS solution, therefore pi-hole cannot be told what hostname the IP belongs to.

I’ve seen a few of these log entries mentioned on the forums so far in my research today, but often the topic ends up closed and I’ve not figured a definitive answer as yet.

Hope that helps somehow.

3

Hi there,

That a good point. However, I don’t use unbound in my install….

That said, I would love if someone one from the dev team could perhaps point to where to look for the issue….

Best regards,

/// Bjarne

4

Please generate a new debug Token.

5

Here you go!

https://tricorder.pi-hole.net/AW0eybtd/

And thanks much for looking into this!

/// Bjarne

6

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