Guidance on Troubleshooting Subtle Networking Problem

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Sep 29, 2020
Excuse me Please:

over last few weeks, maybe a month, frequent intermittent network/DNS connectivity issues are being experienced by my FireFox browser. Also, it kinda feels like the networking problems seem more noticeable in the evening, no so much in mid-day.
note, this a recent and noticeable change to Internet browsing. Sprint WISP modem consistently displays 4/5 signal strength (lessened signal might have been potential cause)
about six months (i guess) ago, I had newly implemented user.js functionality for limiting Firefox's default lack of privacy, tracking removal, improved networking, etc. (copy can be posted on demand) and with such, FF was SCREAMINGLY fast! more so with the Raspberry Pi-Hole also implemented on the network and is SOLE DNS provider many months ago.

just this last few weeks or so, SOMETHING changed. and I am uncertain where to begin testing for something that might be deep in OS, or on ISP side.
additional note about my environment: NOTHING changes, no patches, no versioning, no updates, NOTHING.
so, all things being equal, if the same car is driving on the "same" roads, as it were.

Now, the browser would frequently display a Server not found page, yet spamming Refresh/Try Again causes browser to display "Looking up site..." connect, and display page of site I was just browsing!

I have eliminated as cause:

1. Firefox Sandbox contents {emptied Sandboxie sandbox, reloaded FF as though freshly installed} no change.
2. DNS swapped on TCPIP between both Pi-Hole & direct .3 Cloudflare and back to Pi-Hole, no change.
2a. also used both .1 and .3 CloudFlare on Pi-Hole, no change.
3. user.js adjustments with and without, no change
4. Rebooted PC multiple times, no change
5. all networking equipment powered down each evening, power restored next morning, no change.

Same problem on FFv56 as well as Waterfox v2010.10(64bit) Portable.

I have both of's HTTPS Everywhere (not currently set to FORCE ALL HTTPS) and Privacy Badger, with reminder, these both have been present on install for years without adversity.

DNS on TCPIP as well as IP are both statically assigned.
DNS Service has NEVER been enabled, ever.

I recall (but can not now find the screenshot I took) doing CLI tracert tests to, and strangely, was initially NOT resolving, after a couple attempts would then start to function.

seemingly, it is though DNS is being intermittently blocked (or not responded to) though I do not know what further tests I can run; any tests, or networking testing software, or suggestions greatly appreciated.

it should also be noted that I have also run several different Live CD AV scans on this system, nothing was found.


Active member
Oct 25, 2020
Strange behavior.

So, what exactly makes you think that DNS is not working? You can manually test DNS queries using nslookup at the Command Prompt.

## try and resolve using your default DNS
## this should ALWAYS work

## try and resolve using 3rd party DNS servers

If domains resolve, then DNS should not be a problem.

The ammount of customizations you have on Firefox could be causing some issues. I would consider creating a clean Firefox profile and test your experience without any plugins or modifications.

You don't have to delete your current profile and settings. You can create new ones and use them at the same time. To manage and select profiles, type in the address bar:




Sep 29, 2020
in using nslookup, it seems there is something amiss with Pi-Hole.
However, in looking into their Help forum, it seems they require one to be fully versed in Linux to frame questions in just a right way per their format to even submit.
so, i have a broken pi-hole.
thanks for the nslookup test.
  • Sad
Reactions: Barry Wallis


Nov 15, 2020
In line with JulioHM's FFox profile comment... A troubleshooting step I use is to create a new user profile on the computer and test the issue. If it is resolved - it's likely user profile related - if not, computer / OS / system related or network (outside of the system) related.