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Definite DNS problem

plusenetsteve
Hooked
Posts: 8
Registered: 04-11-2014

Definite DNS problem

We have been having what I thought were line dropouts nearly every evening, which last from a few minutes up to at least 10 minutes (at which point we reset the router). It was because re-setting the router always worked (either by powering down/up or logging in and disconnecting/re-connecting)  that I assumed it was a line fault, which I never got round to reporting. I tried Firefox, Chrome and IE but to no avail.
However, one day it happened during the day. My browser wouldn't connect but I was streaming Radio 4 at the time and this kept working! So I did some pinging, and found that I could ping by IP address but not domain name.
For some reason it didn't immediately occur to me  to try changing my adapter DNS setting from automatic to a public one (Google 8.8.8.Cool, but when I did everything woked fine! So it is definitely a Plusnet DNS issue.
BUT before I start getting asked stalling questions, I experimented. I set my desktop ethernet adaptor's DNS to 8.8.8.8 and when my wife and daughter complained that the wireless had gone down I checked my desktop and it was working fine! I reset the router and changed my laptop's wireless adaptor  to 8.8.8.8 and waited for the next "dropout". Sure enough, when my wife and daughter complained the wireless had gone down again, guess what, my laptop stayed connected! So I changed my wife's laptop to 8.8.8.8 without even closing the browser, opened a new tab and it started working again!. At the next dropout (Sunday 2/11/14) my daughter complained but my wife and I were still connected OK, so I changed her settings to 8.8.8.8 without closing the browser and it was working again!
If this is not a Plusnet DNS problem I will eat my hat! The only puzzling thing is that re-setting the router also seems to work.
       
24 REPLIES
Community Veteran
Posts: 19,101
Thanks: 443
Fixes: 21
Registered: 31-08-2007

Re: Definite DNS problem

Hi plusnetsteve,
Welcome to the forum. Now this is an intriguing problem. I have seen what sounds like identical issues which I have yet to get to the bottom of. (Instead of Radio streaming I was on Skype when I first realised). They are considerably less frequent than they used to be and I did a workaround by changing my TCP/IP settings in Windows to add alternate DNS using both Level 3 and Google.  I have set the order of use so that in normal circumstances it should work as it would automatically My Firewall lets me know if it wants to connect to the 3rd on the list (the first non-Plusnet DNS).
I suspect that this has something to do with the modem/router.
Can you post which modem/router you are using, which model/software version etc. If it's the TG582n, has it got the USB port?
Superuser
Superuser
Posts: 11,889
Thanks: 3,250
Fixes: 22
Registered: 22-08-2007

Re: Definite DNS problem

There is another user with an issue which sounds as though it could be intermittent DNS issues - see http://community.plus.net/forum/index.php/topic,133647.0.html
I wonder if there is any chance this could be related to the new IP address pool - 146.199/16 ?

Steve,
Can you please advise if your IP address (when you have the problem) is in this pool?
Kevin
Community Veteran
Posts: 5,109
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Registered: 10-06-2010

Re: Definite DNS problem

I've got a 146.199 IP address and have no particular problem with plusnet's DNS servers.
There have been threads in the past where the internal DNS proxy server in the technicolor router seems to stop working, because it only seems to affect a handful of people nothing much gets done towards investigating or solving the issue.
plusenetsteve
Hooked
Posts: 8
Registered: 04-11-2014

Re: Definite DNS problem

Hi Anotherone
Thanks for replying.
Router details:
TG582n, no USB port
Software Release: 8.4.4.J
Software Variant:         BV
Boot Loader Version: 1.0.5
At one time I thought it was something to do with entries in my router log like those below, but I ruled that out because they don't occur exactly at the same as the dropouts and are, apparently, very common and show that the router firewall is doing it's job.
FIREWALL icmp check (1 of 5): Protocol: ICMP Src ip: [Remote IP] Dst ip: [My IP] Type: Destination Unreachable Code: Port Unreacheable
FIREWALL replay check (1 of 2): Protocol: ICMP Src ip: [Remote IP] Dst ip: [My IP] Type: Destination Unreachable Code: Host Unreacheable

plusenetsteve
Hooked
Posts: 8
Registered: 04-11-2014

Re: Definite DNS problem

Hi Townman
My IP address is in that pool now but hasn't always been when I've had the problem. One thing I have noticed recently is that my ip address changes more or less every time I reset the router, whereas it didn't at one time even though I've always been on DHCP.
plusenetsteve
Hooked
Posts: 8
Registered: 04-11-2014

Re: Definite DNS problem

By the way, it might be my imagination but since I switched to Google's DNS, web pages seem to load faster, which surprises me.
Community Veteran
Posts: 19,101
Thanks: 443
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Registered: 31-08-2007

Re: Definite DNS problem

Hi plusnetsteve, as you've discovered, nothing to do with log entries (unsolicited probes) - you don't need to redact the Src ip: when posting such info, by the way.  A lot of them seem to come from places like China etc.IMHO it's not a bad idea to have this in the public domain in case it shows more determined probes from specific addresses over time.
Your public IP address will change everytime you change gateway, unless you are on a fixed one.- you can hop gateway (without losing sync) by logging into the 582n and clicking Disconnect in the Internet box - this drops the PPP session - wait about 30 seconds and then click Connect.
@ejs
Well we are on the case now ejs Wink and your description seems to fit the bill - I'll post up some interesting ping graphs later if I can find them (ie weren't on my crashed drive)
But what are the circumstances that cause it to stop - it is for a limited period - if one can get closer to that, then we might be halfway to a solution.
Anyway, nothing whatsoever to do with IP address as I've experienced it with a multitude of IP addresses across the different gateways. However, Townman's comment has led me to think to note which gateway from now on. Although I don't believe this is gateway specific, the circumstances might possibly be related to the data centre the gateway belongs to - might be a red herring but worth noting in case there's a pattern.
Another thought - do a tracert to ntp.plus.net and keep that as well and see if any pattern emerges -
A couple of weeks back I'd noted that for some time across a variety of gateways the number of hops was the same, whereas many moons back, that could vary depending on gateway/data centre. After my issues a couple of days ago, I was surprised that on reconnection (to a ptn gateway) there was 2 extra hops which hadn't been the case when I'd previously been on that gateway. Also the ping was [Censored] (historically it used to be one of the poor ones for me, but as I implied that seemed to have changed, I shall keep notes again from now on.)
Community Veteran
Posts: 19,101
Thanks: 443
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Registered: 31-08-2007

Re: Definite DNS problem

Now, just to go back to the 582n and software/firmware release etc. Whilst there is a latter version suitable - it does not IIRC from my testing make any difference to this issue BUT before anyone suggests you upgrade the firmware, unless you are having any other problem with your connection affecting sync then DON'T upgrade for the time being. It will be interesting to collect some data first. I'll suggest some more tests a bit later, when I've dug through what I can find here.
Ah, one other question, are you on a 20CN or 21CN connection? Actually if you can post the TG582n Full DSL stats that'll give us some info about the exchange card as well.
plusenetsteve
Hooked
Posts: 8
Registered: 04-11-2014

Re: Definite DNS problem

Hi Anotherone
I'm pretty sure it's NOT 21CN. Stats below. My wife says if she didn't have me to sort things out she would get rid of most of the technology in the house!
DSL Connection	
Link Information

Uptime: 2 days, 13:05:25
DSL Type: ITU-T G.992.5
Bandwidth (Up/Down) [kbps/kbps]: 1.084 / 9.525
Data Transferred (Sent/Received) [MB/MB]: 482,26 / 234,06
Output Power (Up/Down) [dBm]: 12,6 / 0,0
Line Attenuation (Up/Down) [dB]: 24,1 / 42,0
SN Margin (Up/Down) [dB]: 6,1 / 3,8
System Vendor ID (Local/Remote): TMMB / ----
Chipset Vendor ID (Local/Remote): BDCM / IFTN
Loss of Framing (Local/Remote): 0 / 0
Loss of Signal (Local/Remote): 0 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): -
Error Seconds (Local/Remote): 502 / 0
FEC Errors (Up/Down): 840 / 33.054.060
CRC Errors (Up/Down): 379 / 1.488
HEC Errors (Up/Down): 536 / 37.756
pwatson
Rising Star
Posts: 2,468
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Registered: 26-11-2012

Re: Definite DNS problem

I also remember reading threads about the router DNS relay stopping working.  You can prove if it's Plusnet's DNS server or the router by manually specifying  PN's server on a test PC (just as you've done for testing with Google DNS).  If the test PC works but other devices don't in this condition, it's the router's relaying function that has failed.
Community Veteran
Posts: 19,101
Thanks: 443
Fixes: 21
Registered: 31-08-2007

Re: Definite DNS problem

That' another way of doing some checks pwatson, but I'm not sure one can be certain about the conclusions being drawn, I really need to find this old data (which will take a bit of time) IIRC it's more complex as it seemed to affect  modem/router behaviour.
Well the good news plusnetsteve is it is 21CN. Ha SWMBO - another one living in the dark ages, I know the feeling. Cheesy
We won't side track on stats for the time being, not too bad for the line length, could be slightly better and errors a bit lower, but we'll come back to that later on.
IFTN line card, shouldn't be any real issues there to the best of my knowledge.
Community Veteran
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Registered: 10-06-2010

Re: Definite DNS problem

An older thread on this issue is http://community.plus.net/forum/index.php/topic,124871.0.html (and contains links to a couple of other threads).
Community Veteran
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Registered: 31-08-2007

Re: Definite DNS problem

Thanks for digging that out ejs, I've bookmarked http://community.plus.net/forum/index.php/topic,118268.0.html mentioned there. There's more than a bit of bedtime reading in that lot  Shocked
Community Veteran
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Registered: 21-01-2013

Re: Definite DNS problem

Plusnet's DNS servers are much improved since that thread.
Plusnet, issue both their dns IP's to the router with a metric of 10. This means the router relays dns lookup to both IP at the same time. I don't see the point of this and wonder if this could be part of the problem. IIRC other ISP have a different metric for each of their servers, the second IP only being queried if the first fails to reply.
It's possible to assign the WAN dns addresses to the network devices via DHCP, this way the routers dns relay is not used. This may be one workaround.
http://npr.me.uk/changedns.html ; method 2)