DNS service is not working

energingfs

I want explication for this problem

gw68

DNS converts human-readable computer/server names into numeric addresses which are what can then be routed through the network. It's very nearly critical for how the internet works (it can work with just the numbers alone, but that's very limiting indeed). Virgin recently suffered from a problem routing requests to DNS servers whilst their network was recovering from an outage.
DNS is also one of the times when you need to know a number instead of a name, for obvious reasons. Google's DNS server is easy to remember for testing purposes. It's 8.8.8.8

trevorh

Fing tells me: DNS service is not working: test domain cloudflare.com not resolved
but it is not true. I can get to cloudflare.com in my browser.
Why does Fing say there is a problem, when there is not?
Regards,
Trevor

gw68

Weirdly my comprehensive reply has vanished.
It short, your browser may be using a different DNS to your system, which is the one Fing would be testing. DNS outages can also be quite short-lived.

trevorh

Hi gw68. I saw your comprehensive reply before it dissappeared. Thanks for taking the trouble - it is a shame it vanished!
I am running Fing Desktop on a MacBook Pro with the latest macOS Catalina release. I had some trouble over the last few days with my Virgin Media Business Broadband, but it is now working fine.
Fing reported the DNS issue at 5:34 this morning, having decided everything was working at 4:32.
I have no DNS servers within my network and I can ping cloudflare.com successfully, as well as browse to it.
I therefore can't understand why Fing thinks it can't resolve cloudflare.com. It looks like a bug in Fing.
Regards,
Trevor

gw68

I regularly get overnight reports of problems with my Virginmedia domestic broadband. I suspect Virgin regularly reboot their equipment in the dead of night. The problems are usually a mixture of DNS issues and loss of connectivity to google.com, and they do seem to come in patches. Some days nothing at all, others 3 or 4 times overnight. DNS issues tend to get reported first as it's earlier in the test sequence I think, making them more prevalent in the report. Also Fing only runs a test periodically, so there may be something coincidental with the timing of a reboot script, say, at Virgin's cable head and when you last rebooted/ restarted Fing.
I also run a mainly Mac set up. The Windows PC I tend to shutdown when not in use as it's a bit more energy hungry (OK, a LOT more!), so I've not got a comparable experience with the Windows version of Fing's desktop application.

trevorh

Hi gw58,
I deliberately refreshed the Fing report and cleared my DNS cache before reporting this issue. Recent refreshes have caused Fing to test ieee.com and microsoft,com. Fing cannot resolve them either, even though I can ping them successfully.
This is a bug in Fing.
Regards,
Trevor

Robin_Ex_Fing

Hi @trevorh
Can you share the screenshot of the report? The alert refers to the DNS not responding at that point of time. If you refresh and rescan the network and still face the same issue, please let me know.

gw68

Well that does look suspicious indeed! All's working well for me at the moment, though. I use cloud flare's DNS by default myself, so it might not show up as often for me.

trevorh

Hi @Robin,
I now have a clue about what is going on. My MacBook Pro is connected to my network with an Ethernet cable, but I also have wifi enabled, because otherwise handoff to & from my iPhone and iPad do not work.
The DNS issue was reported when Fing said the machine was connected by the Ethernet connection. For some reason, it decided at 10:26, about 20 minutes ago, that the wifi connection has joined the network. My MacBook Pro is now reported as being on the wifi, and the DNS issue has gone away. Fing had been reporting that I was on the Ethernet connection for many days.
Having joined the network with wifi, my ISP is misreporterd as Hydra Communications, when it is really Virgin Media, but that might be related to me enabling NordVPN.
If I turn off wifi, I can still ping all the DNS test sites that Fing said could not be resolved.
All of these reports are after refreshing Fing, so they are not left over from previous incidents.
Regards,
Trevor

gw68

It's nice to see NordVPN is working as expected then! 

trevorh

Hi @robin,
While I was away from my MacBook Pro, Fing reported connectivity problems at 14:18 BST, about thirty minutes ago. At 14:21, it reported that DNS resolution is not working. My network connection had switched back to the wired connection, which Fing reports as "Connected via Ethernet at 1 Gbit".
So, every time the MacBook Pro decides it is on the wired connection, it reports that DNS resolution is not working, even though it is.
Once it decides it is connected on wifi, the issue disappears.
It may well be that the wifi goes to sleep when I am away from my machine, then eventually wakes up again, once I am using it.
Regards,
Trevor

Robin_Ex_Fing

Thanks @trevorh
Is the error appearing with both Wired and Wireless connection to your MacBook? Also, Was the computer in sleep mode during that time?

trevorh

Hi @Robin,
I was using my machine at 16:01 when it reported I had connectivity problems on the wired connection. At 16:10, it reported that DNS resolution was not working.
It appears that this error is only reported on the wired connection, but the machine does not have to be asleep.
Regards,
Trevor

Robin_Ex_Fing

Thanks @trevorh
Can you please share the healthcheck report with me privately when connected to Wired connection? 

N4CER

I am having the same issue as Trevor - Fing Desktop throws a "DNS resolution is not working", yet I can get to multiple Internet sites with no problem. I can even run the speed test on the same page as the connectivity warning. BTW, I get anywhere from three (3) to 15+ "DNS connectivity warnings" per day.

N4CER

Question: if possible, how can I disable alerts or service checks on a per-item basis? For example, since I am getting so many false connectivity alerts from DNS, how can I disable this check and subsequent alerts?
Thanks!

Robin_Ex_Fing

Hi @N4CER
Next to the warning, there is a small question mark icon that explains the warning and also provides you with an option to disable the particular alert. I hope it helps.

N4CER

Thanks for the attempt, Robin, but there isn't any small question mark icon. Nor is there any clickable link in the message, I've included a screen shot for reference.
Thanks again, any assistance is appreciated.

N4CER

Disregard my last message Robin, I've found the notification and its small question mark. I've successfully muted the alert and am good for the moment. BTW, the option to disable/mute a notification appears to be available when accessing notifications via the system report. It does not appear if you view through the Notifications tab.