[Solved] piHole seems to work for a bit, then get DNS address not found

Help
1

Just installed Pi-hole on an old modelB-rev1 with 256MB(?) ram on 32gB SD card (8% used)

Router is a tp-Link AX3000 4-stream wifi-6

  • Operating System = 32-bit Raspbian GNU/Linux 13 (Trixie) OS-lite version
  • new install of OS, then ran sudo apt update && sudo apt upgrade
  • then installed using sudo curl -sSL https://install.pi-hole.net | bash
  • nothing else is running on the pi
  • RaspController app actually reports RAM as 173Mb with 68Mb as spare - pihole debug log also says memory 173MiB System memory

Actual Behaviour:

Everything installed OK - set the router DNS to the pi-hole static IP

Pi-Hole console seems to be working fine with queries being shown & graphical display etc

However after loading a couple of web-pages I start getting DNS address not found

Switch back to the router's original DNS addresses (not pi-hole) and it all works OK again

Switch back to the pi-hole DNS ip and then start getting DNS address not found after loading a couple of successful pages

Running nslookup from the laptop command prompt returned this - DNS timeout without the pihole IP, but works with the pihole ip

C:\nslookup google.com
DNS request timed out.
timeout was 2 seconds.
Server: UnKnown
Address: 192.168.1.254

DNS request timed out.
timeout was 2 seconds.
*** Request to UnKnown timed-out

C:\nslookup google.com 192.168.1.95
Server: pi.hole
Address: 192.168.1.95

Non-authoritative answer:
Name: google.com
Addresses: 2a00:1450:4009:c17::65
2a00:1450:4009:c17::71
2a00:1450:4009:c17::8a
2a00:1450:4009:c17::8b
142.251.30.113
etc...

Further {edit} used Google AI which said to

  • leave the router's WAN/Internet DNS to "Get Automatically from ISP"
  • in the DCHP settings, set primary DNS to pi-hole leave secondary DNS blank
  • nlslookup now returns this - with pi.hole as the server, not the router

nslookup google.com
Server: pi.hole
Address: 192.168.1.95

Non-authoritative answer:
Name: google.com
Addresses: 2a00:1450:4009:c17::8b
2a00:1450:4009:c17::65

etc

Any ideas?

So my DCHP changes look to have fixed it :crossed_fingers: - it would be great if someone with a bit more understanding could confirm this is now correct ...TIA

Cheers, G

{edit} - suspected it might be RAM size issue (free -h showed 1.7Mi with corresponding 1.7Mi swapfile size, so I've increased the Swap size to 1.0Gi (and rebooted) hoping that might help, but still getting DNS address not found {/edit}

Debug Token:

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

2

What machine on your network is at 192.168.1.254? Because the client you ran nslookup from is trying (and failing) to use that .254 machine as a DNS server.

Either your client machine is configured to use .254 using a static DNS assignment, or DHCP is telling it to use .254 for DNS.

The way to fix this will depend on where your client device is getting the .254 as DNS.

3

.254 is my router's IP address = default gateway

Many thanks - I've just added some more information in my original posting above, which may have fixed it, with suggestions from Google AI which said to

  • leave the router's WAN/Internet DNS to "Get Automatically from ISP"
  • in the DCHP settings, set primary DNS to pi-hole IP leave secondary DNS blank

Could you just check what I've written please, and see if it makes sense. TIA

4

Assuming you're using IPv4 only on your LAN, that should fix it for you. Plus it will keep all that router noise out of your Pihole logs. :slight_smile:

5

Brilliant - that's a great help: thanks for confirming this as I'm not that familiar with network/DNS routing etc

Cheers, Geoff