Diagnosing intermittent "can't find IP" errors

DaveC426913

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Summary
How do I diagnose the cause of intermittent 'IP could not be found' errors?
This started a couple of days ago. It is very sporadic, but comes and goes in waves.
I'll open a page such as facebook, physicsforums or any of a bunch of sites I visit regularly. I get this:

This site can’t be reached
www.facebook.com’s server IP address could not be found.

Try:
DNS_PROBE_FINISHED_BAD_CONFIG


Try again 30 seconds later and it's fine. Go to another site, get similar result, wait 30 seconds, it's usually fine.

  • Using Chrome on Win 10 laptop, with Wifi.
  • have changed nothing about my system or my setup any time recently
  • do occasionally cycle my router
  • Speed test: not great, but not abysmal - getting at least 10+Mbps download
  • ping: will often fail (cannot find host)
  • tried various sites - does not seem to discriminate
  • asked friends (no one else seems to be experiencing this)
  • (have not phoned my ISP yet)
  • (have not messed with any DNS settings yet)
Suggestions on how else I can narrow down the problem?
 
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I think this is due to not connecting to a DNS server for a lookup of the address.


has some troubleshooting tips.

So maybe you could locate the addresses of your DNS servers and then do ping tests on them too.

Also its likely a timeout issue:

1) broken internet connection (bad wire connections, water in the connection, wire damaged by yard work, age and weather ie water got in somewhere)

2) slow internet connection (ie slow enough that it expires on your end after your request)
2.1) bad connection causing retries

3) Streaming going on through your connection (someone watching a movie or kids playing games)

4) Firewall issues on your end

5.1) Someone stealing your internet wirelessly or otherwise
5.2) Some kind of man-in-the-middle attack that is slowing things down with an extra hop
 

DaveC426913

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1) broken internet connection (bad wire connections, water in the connection, wire damaged by yard work, age and weather ie water got in somewhere)
I've done speed tests. It seems pretty normal throughput.
And I occasionally get the errors on other sites even while the speedtest is showing A-OK.

When I ping, I get very normal times: no more than 30ms.

3) Streaming going on through your connection (someone watching a movie or kids playing games)
Nope. Just me.

4) Firewall issues on your end
Maybe, but nothing has changed.

5.1) Someone stealing your internet wirelessly or otherwise
Maybe, but if that were true, I should see a corresponding drop in my throughput.
Also, restarting the router, in an attempt to boot them off, doesn't seem to help. (which means they'd have to have broken my password).

Slow or intermittent connection.
Doesn't seem to be on my end.
 

Klystron

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Seems primarily a DNS issue; the server names are not resolving to TCP/IP before timing out.

I saw a few similar errors last week while connecting; first login to PF for instance.
Mozilla Firefox on Windows 8.2.
Windows auto-updated as did Firefox. I closed and re-opened Firefox to install latest updates.
Have not seen this problem since.

[Edit: almost forgot also purged cache and cleared browser history, Ran CCcleaner to snag any remaining cookies while Firefox and Chrome not active. --Norm]
 

DaveC426913

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Seems primarily a DNS issue; the server names are not resolving to TCP/IP before timing out.
I'm used to timeouts happening after a sufficient interval - many seconds.

These are occurring virtually immediately - within two seconds or so.
 

Klystron

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I'm used to timeouts happening after a sufficient interval - many seconds.

These are occurring virtually immediately - within two seconds or so.
Well just guessing but seems as if some info might be cached. Browser may be using some old cached info instead of actual DNS query. Some times Task Manager or Resource Manager can show the actual DNS query. I use CCleaner as well as native settings to eat those old cookies and stuff after closing the browsers.
 

Klystron

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@jedishrfu 's list of connectivity checks rings very true to me. After a major flood in 2003 my network, phone and Internet connections were rife with various inexplicable errors. Sprint etc. refused to trouble-shoot from the end of the block to my house. Phone company even added new repeaters giving me a very fast noisy connection. After much grief my next-door neighbor finally reported identical problems.

The cables running from the street to the utility cabinet in front of our houses were full of dirty water. Simple repair fixed all.
 
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We had the issue of water getting into the buried connectors.

One time while doing yard work I mistook the cable for a root and chopped it. I then had to splice it back and seal it but over time water ruined the connection, introducing errors in transmission and thus timeouts became more common.

Finally the cable company came and reran the cable, they don't diagnose to that level so now I have an old and a new cable making it 50/50 that I accidently cut it again. (they are buried only an inch or so deep, hey its Texas and limestone prevails)
 

Klystron

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Kudos for admitting your error in unintentionally severing the cable. Nevada backyards are built on caliche. I ran above ground swimming pools not just from cheapness. Pool builders did not think they could get the digging rig they needed through the existing fences. Dynamite was not considered a useful option in an established housing tract :smile:.

The 2003 flood was awesome. I led a convoy of pickup trucks and SUV's from DOE headquarters north to high ground above Centennial Park. The DOE local Summerlin data center not only flooded, a wall partially collapsed from outside water pressure. Existing water pumps tried and failed to keep roads passable. I almost entered an intersection that appeared to be inches deep until I saw the top of a fire truck barely poking above the torrent. Another fire truck floated past sideways (filmed by local news station on Gowan Road.). Naturally, my truck was brand new and I had moved to my new house two days before the thunderstorm. Truck, house and Yours Truly survived unscathed

Flooding lasted for three days. Underground utilities took much longer to drain. The problem for my house connections appeard to be storm runoff forced into plastic conduits in concrete culverts below street level right outside my property.
 
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We have a saying in Texas for low water crossings:

Turn around, Don't drown.

Too many people try to cross what they think is inches of water only to discover too late that portions of the road have washed away.

In one case recently, folks living in a subdivision near a Lake Travis (one of our highlands lakes ie flood control lakes) had to canoe supplies in because the water was over the roadway for several hundred feet. It took a couple of weeks for it to finally subside due to water upstream still draining to the Gulf.
 

phinds

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Dave, I've had that kind of situation twice. Once it was my local ISP that was flaky for a while (but they fixed it pretty quickly) and the other time it was, and I'm not kidding, squirrels having chewed on the cable wire where it ran to a utility pole at the edge of my property. That one caused several problems, mostly w/ the TV and I had to get a Time Warner guy out to track down the problem. The squirrels had a nest up in the pole and the TW guy said they were not allowed to destroy the nest, they just had to fix the cable and hope it didn't happen again (it didn't, which surprised me)
 
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DaveC426913

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Right but if it were a local connectivity/network issue, as you're all suggesting, I should be seeing signs of that in my speed tests.
 

DaveC426913

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Well just guessing but seems as if some info might be cached. Browser may be using some old cached info instead of actual DNS query. Some times Task Manager or Resource Manager can show the actual DNS query. I use CCleaner as well as native settings to eat those old cookies and stuff after closing the browsers.
This would certainly explain why these error pages are coming up virtually instantly, instead of after ten seconds or so, as they ought.

It's like my browser isn't even trying.

Browser: "Yeahyeah. Failed again."
Dave: "What? You didn't even check!"
Browser (rolls eyes, puts down Twix bar): "Oh sorrrrrrieee. There. I checked. Happy?"
 
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Dave, I've had that kind of situation twice. Once it was my local ISP that was flaky for a while (but they fixed it pretty quickly) and the other time it was, and I'm not kidding, squirrels having chewed on the cable wire where it ran to a utility pole at the edge of my property. That one caused several problems, mostly w/ the TV and I had to get a Time Warner guy out to track down the problem. The squirrels had a nest up in the pole and the TW guy said they were not allowed to destroy the nest, they just had to fix the cable and hope it didn't happen again (it didn't, which surprised me)
I guess they were hoping to see Alvin and the Chipmunks but TW wasn’t carrying that channel.
 

phinds

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Right but if it were a local connectivity/network issue, as you're all suggesting, I should be seeing signs of that in my speed tests.
Yes, I think that's true.
 

Klystron

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Right but if it were a local connectivity/network issue, as you're all suggesting, I should be seeing signs of that in my speed tests.
Possibly. Probably depends on the test and query format.

While I was having the previously mentioned water problems, traceroute or ping, say 'ping microsoft.com' I might receive a DNS error 'server not found'. Network speed was fine even fast. But packets would get munged and VOIP conversations included high-pitched warble, hum, and cross-talk. Cable TV downloaded fast with adequate bandwidth then might suddenly display digital artefacts and Freeze. It became a "thing" in our household to guess what and when the feed might freeze.

All problems fixed when the wet cables under the street were finally replaced.
 

StoneTemplePython

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Do you use AT&T for internet per chance?

I had something like this a while back...

It and a few others are notorious for this. And it was peculiar -- problems with standard pc connections, but no problems e.g. with connections on iphone or roku (and supposedly no issues on macs).

  • Using Chrome on Win 10 laptop, with Wifi
In any case the 'out of sample' test is to try internet connectivity on some other non PC device, maybe iphone or ipad is ideal .
 

Tom.G

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I've been having the same/similiar symptoms here in Southern California the past week or so. It crops up a few times a year, lasts a day to a couple weeks, and self-corrects. Apparently some DNS look-ups fail and a connection is not completed in a timely manner. Usually, but not always, just hitting the F5 key (retry) on the kbd gets results. The ISP here is Charter Cable, aka Spectrum.

If you want to narrow the problem to You/Internet, you can use the WIRESHARK program to capture and see every data packet that goes thru your computer network connection.

Please keep us updated on the situation.

Cheers,
Tom
 

Svein

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I tend to use 8.8.8.8 as a secondary DNS server. It usually knows the answer.
 

DaveC426913

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After clearing my browser cache the problem appears better, though it has not gone away. So it might just be a coinky-dink that I'm getting good connection right now.
 

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