DNS Failure (Across my house) Every 15-30 minutes for about a minute.

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cookiesbeware

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Apr 19, 2015
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Title sums up the problem pretty easily, can't connect to anything but existing connections will stay open, like Skype calls and such.

I have tried two routers:
Belkin N150
Linksys E3000

Two modems:
ubee U10C035.30 D3.0
ARRIS / Motorola SurfBoard SB6121

All devices on network have been affected:
Smart phones - Android+Apple
Computers - Win 7+8.1

ISP:
Xfinity - Cable @ 50mbps down, 12mbps up

I have powercycled, change cables, tried just hooking up to modem, and even called Xfinity customer service (Where they didn't see a problem when they checked it, so they told me everything was fine).

The period of time usually is around 30sec-1min. The frequency in which it happens varies, I've had it as quick as 5 minutes, but I may not be noticing times it does go out due to not opening a web page or something similar.

Would love suggestions as to where I should direct my attention to fix/troubleshoot this problem.

Edit: I've tried Comcast's and Google's DNS servers and got the same problem.
 
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The two times I've contacted them I've gotten the general customer support run around where they check things according to their checklist and resets. Saying it's all clear and then I get the issue a little later after I'm done with them.
 
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I should probably also mention I've tried both Xfinity's DNS servers and Google's DNS servers, and received the same problem.
 
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Then that would point to a physical issue, outboard of your modem. Cabling, or one of their upstream boxes.

Here's what you do:
Keep a detailed log of when it happens and for how long. See if you see a pattern. Time of day, same times every day, outdoor temps, stuff like that.
Try to call when it is actually broken.
 
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Their DNS servers are having a problem not you equipment.
What you can do is add more DNS servers to your routers or modems DNS servers list.
I get the same problem with windstream, my only option.
Add 8.8.8.8 and 8.8.4.4 for googles dns servers.
Open dns servers 208.67.222.222 and 208.67.220.220


 
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You're 100% sure it's *just* DNS and not your entire connection?

Can you run a ping, something like: ping -t www.google.com
Just leave it running.
When your DNS drops out does the ping keep working (it should, even though you've used the name (google.com) it'll only resolve that once and then use the IP Address from then on)
If it is JUST a DNS issue your ping should keep working through it, but if it's your entire connection the ping should stop.

Sorry if you've been there done that and I'm telling you things you already know, but you just don't want to be wasting your time chasing a DNS issue if it's actually a larger connection problem.
 
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I have had this problem for approximately 3 weeks, and very consistent happening anywhere from 5-30 minutes, but I will try and keep a log of it if I can.
 
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I've had skype calls and game sessions remain in contact and working if that answers the ping question. I have it running to answer your question fully when I have problems again.
 
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You can hope the ISP is not being a butt head and routing all dns to their server no matter what IP you use.

Another trick you can try if you really think it is only dns is find some addresses of some common servers you use and put them in the host file in your pc. This will force the pc to use the local file to look up the ip rather than dns. Some sites you can also just key the ip into the browser bar directly.
 
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**UPDATE** -> I left a remark in there which has now been corrected... If you caught the earlier version use this one instead....

OK, a did a little script up for you which will help you isolate the problem... I'll put it at the end.

What it does, every 30 seconds (looped 60 times), it will attempt to lookup www.google.com using 4 different DNS servers:
1) your default (presumably your home router)
2) your ISP DNS server (YOU NEED TO SET THIS IN THE SCRIPT BELOW
3) OpenDNS server
4) Google DNS server

It spits the results out into a TXT file which you can then examine for the problem. It'll run for half an hour. When it's done you can open the txt file, find the point at which your DNS fails, and you should be able to then see which DNS servers are failing at that point. Is it JUST your home router, or is it your ISP, or ALL of them? If you have that information it will help you pinpoint the problem.
I'd be running a ping -t as above at the same time just to eliminate any potential internet drop outs as a issue (though I fully agree, Skype and games does eliminate that too... but you're trying to gather evidence here and a ping -t doesn't lie!)

With the text below you need to...
a) create a new "Text Document"
b) Open it with Notebook
c) paste in the text below (below the "---")
d) replace the **YOURISPDNS_IP_HERE" text (about 2/3rds of the way through the script) with ONE of the IP addresses for your ISP's DNS servers (that should be in your router status pages if you don't know it)
e) save the changes and exit notepad
f) Rename the file from a .txt TO a .bat file (you may need to change your folder view in the options by UNTICKING "hide extensions for known file types"... or you can rename it in a command prompt. Post back if you need help with this step.

That's it, once it's a .bat file, just double click on it to run it and it should sit there polling the DNS servers 60 times with a pause between tests.
DISCLAIMER: I'm not a programmer or scripter really, so I'm sure someone who knows what they're doing could produce something more elegant. But I tested it and it works for me... Here's the script.

---
#!/bin/bash

REM this script tests DNS connectivity a specified of times, pausing a specified interval between tests...
REM it outputs the results to the file DNSTestLog.txt

REM set the number of loops AND pause interval between tests (in seconds)
set /a TotalLoops=60
Set /a PauseInterval=30

Set /a LoopCount=1

:loop
If %LoopCount% gtr %TotalLoops% GOTO END
ipconfig /flushdns
echo TEST NUMBER %LoopCount% >> DNSTestLog.txt
echo %time% >> DNSTestLog.txt
echo ROUTER DNS >> DNSTestLog.txt
nslookup www.google.com >> DNSTestLog.txt
echo ISP DNS >> DNSTestLog.txt
nslookup www.google.com **YOURISPDNS_IP_HERE >> DNSTestLog.txt
echo OPENDNS >> DNSTestLog.txt
nslookup www.google.com 208.67.222.222 >> DNSTestLog.txt
echo GOOGLEDNS>> DNSTestLog.txt
nslookup www.google.com 8.8.8.8 >> DNSTestLog.txt
echo --- >> DNSTestLog.txt
set /a LoopCount=%LoopCount%+1
TIMEOUT /T %PauseInterval%
GOTO LOOP

:end
 
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Alright. Not sure what happened considering I was having problems across the entire house, but after I ran your script on just my desktop I haven't had a single problem since. Would using flushdns do anything that might have fixed the problem? I'm curious as to what was fixed now. And I'll update this if I do have the problem return.

Scratch that. A minute after posting I get the problem again. And ping -t google.com was timing out.
 
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to test if it is their server problem you can ping the DNS server.
ping ???.???.???.??? -t where the ??? is their dns servers address.
you can also ping Google or open dns servers.
google ping 8.8.8.8 -t or ping 8.8.4.4 -t
open DNS ping 208.67.222.222 -t or ping 208.67.220.220 -t
if your ISP times out and google or open dns servers respond it is a problem with their dns servers.
You can have multiple CMD windows open pinging multiple servers or addresses.

Using ping www.google.com -t means you have to connect to their dns servers first to get the ip address for google.
And in case you did not know the -t means to repeat for as long as the CMD window is open.
 
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Except that not all DNS servers will respond to pings. I know my ISP's DNS servers do not answer pings.
 
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I'm going to assume that it is a hardware problem outside of my house based on the results and responses you all gave me. I'll update and answer this topic once I get it resolved and post the outcome.
 
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