Intermittent DNS failures with pihole running on 3B+

#1

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Expected Behaviour:

Pihole reliably resolves DNS requests without timeout.

Actual Behaviour:

Pihole intermittently stops resolving requests, causing ping timeouts an loss of internet access (or more clearly, SSID still broadcasts but I’m not able to browse anywhere).

Ping stats:

ping 8.8.8.8 -t
Pinging 8.8.8.8 with 32 bytes of data:
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Reply from 8.8.8.8: bytes=32 time=14ms TTL=121
Reply from 8.8.8.8: bytes=32 time=17ms TTL=121
Reply from 8.8.8.8: bytes=32 time=27ms TTL=121
Reply from 8.8.8.8: bytes=32 time=13ms TTL=121
Reply from 8.8.8.8: bytes=32 time=17ms TTL=121
Reply from 8.8.8.8: bytes=32 time=13ms TTL=121
Reply from 8.8.8.8: bytes=32 time=14ms TTL=121
Reply from 8.8.8.8: bytes=32 time=14ms TTL=121
Reply from 8.8.8.8: bytes=32 time=32ms TTL=121
Reply from 8.8.8.8: bytes=32 time=14ms TTL=121
Reply from 8.8.8.8: bytes=32 time=13ms TTL=121
Reply from 8.8.8.8: bytes=32 time=12ms TTL=121
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Reply from 8.8.8.8: bytes=32 time=25ms TTL=121
Reply from 8.8.8.8: bytes=32 time=15ms TTL=121
Reply from 8.8.8.8: bytes=32 time=119ms TTL=121
Reply from 8.8.8.8: bytes=32 time=15ms TTL=121
Reply from 8.8.8.8: bytes=32 time=13ms TTL=121
Reply from 8.8.8.8: bytes=32 time=15ms TTL=121
Reply from 8.8.8.8: bytes=32 time=18ms TTL=121
Reply from 8.8.8.8: bytes=32 time=15ms TTL=121
Reply from 8.8.8.8: bytes=32 time=13ms TTL=121
Reply from 8.8.8.8: bytes=32 time=16ms TTL=121

This issue is happening frequently, although I haven’t found a way to reproduce it.

Other notes:
I am using a Netgear R7000 with the DNS server set to only my pihole (192.168.1.31). DHCP is still being handled by the router, and I’ve assigned the pihole that IP address statically.

My pihole is wired directly into my router via ethernet, and as far as I can tell, WiFi is not enabled on the pihole.

Debug Token:

zzoh20k7g3

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#2

You’re pinging an IP address and not a DNS name so there is nothing that Pi-hole is involved with. This is a network issue and not something that we would be causing.

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#6

Thanks for getting back to me so quickly, Dan!

Forgive my ignorance, I’m very new at everything networking. Is there a specific DNS name that I should be pinging for Google’s DNS servers other than 8.8.8.8?

I’m not 100% convinced this isn’t a pihole issue, as reverting my DNS server on my router to ISP provided immediately resolves the issue and I have no ping timeouts.

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#7

Since the only thing that Pi-hole does is convert DNS names to IP addresses you can use dig for testing the application. dig google.com @<pi-hole.ip> using the internal IP address that you are providing to your clients as their DNS server. Pinging doesn’t reveal information about the performance of Pi-hole much in the same way that mapping potholes in the street wouldn’t reveal much about the state of your cars engine.

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#9

That’s a great analogy, thank you.

Here’s the response for the dig command while the issue is not occurring, everything looks good to me. I’m going to see if I can get another when it’s acting up, but due to the intermittent nature of it, it may be a while. Otherwise I’ll chalk it up to ISPs being ISPs (-:

> dig google.com @192.168.1.31
> ; <<>> DiG 9.10.3-P4-Raspbian <<>> google.com @192.168.1.31
> ;; global options: +cmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 47978
> ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
> 
> ;; OPT PSEUDOSECTION:
> ; EDNS: version: 0, flags:; udp: 512
> ;; QUESTION SECTION:
> ;google.com.                    IN      A
> 
> ;; ANSWER SECTION:
> google.com.             145     IN      A       172.217.6.110
> 
> ;; Query time: 26 msec
> ;; SERVER: 192.168.1.31#53(192.168.1.31)
> ;; WHEN: Wed Feb 13 00:06:26 GMT 2019
> ;; MSG SIZE  rcvd: 55

Thanks again for the help.

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closed #10

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