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Troubleshooting Psychosis: router LCP down, loss of sync

myredhotcar
Grafter
Posts: 457
Registered: 06-11-2013

Troubleshooting Psychosis: router LCP down, loss of sync

Hello. This is my first post. Before I begin, when I say "troubleshooting psychosis" it sounds like what I am looking for is a doctor but I actually require router advice.
My connection was switched on yesterday so I set up my DG 834G v3. The internet came on but only for a few minutes and it cut out. I checked it had the latest firmware, checked settings and restarted. The internet came on but only for a few minutes and it cut out. I checked the logs and I was getting LCP down followed by loss of sync every 1-6 minutes. I left it on and these errors occurred solidly with a tedious predictability. I tried three splitters and two modem cables with no success, and took the bottom plate from the BT socket (I have 1), exposing the master socket with true optimism which turned out to be misplaced.
After a solid day of all this, interspersed with lots of reading online about - and changing - settings I don't understand and running up and down the stairs to look at lights on the router constantly I am whacked. But troubleshooting requires lots of caffeine, and kegs of energy drinks are BOGOF, so I can't sleep. I did more troubleshooting and more kegs of energy drink. Did a bit of running about with splitters and cables. Ran past a mirror with some cables and realised I looked haunted by network problems and caffeine.
After verifying my router worked at a neighbours (it did) I realised I actually had a spare router. I wasn't confident when I unboxed it as it is unbranded but I plugged it in and it's been running solidly even though some of the options are misspelled in the web interface.
Why would my trusty years old Netgear fail (despite working over the road), to be usurped by a nameless upstart that appears to have been given away with teabag vouchers? Is it dying or could there be some form of minor fault that this router ignores? Anyone?
94 REPLIES
Community Veteran
Posts: 5,472
Thanks: 292
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Registered: 11-08-2007

Re: Troubleshooting Psychosis: routers

@'myredhotcar' -

Welcome to the forum !  Cool

Until recently I used to buy second hand Netgear DG834GT modem/routers of eBay and then 'flash' them with DGTeam firmware,  which I would then install for friends, family, and neighbours as a cheap, reliable, and great performing little internet boxes.
One thing I did notice with these, is that the mains power adaptors were the weakest component, and would sometimes output a lower voltage than expected - causing the modem/router to not perform as it should.
If you have a volt meter, you can easily check the DC output of the PSU,  and if faulty then replacements are cheap, or being a common voltage and plug size you may be able to find a disused mains adaptor that you have already.
You might also want to try running RouterStats on your DG834 and monitor whether your modem is seeing wild variations in noise margin, etc  - the graphs might just give you a clue as to what is going on.
With any router that is misbehaving, I would recommend resetting the thing back to factory settings (using the 'default' button on the back), and then reconfiguring it from scratch.  You never know it might just fix it.
Good luck  Wink
myredhotcar
Grafter
Posts: 457
Registered: 06-11-2013

Re: Troubleshooting Psychosis: routers

Hi Purleigh, and thanks for the welcome!
I sourced a brand new replacement Netgear power adapter with no change. I also tried an adapter with identical voltages from a different router, also with no success. I have tried hard resetting the router a few times now.
I signed up with Plusnet at the same time as a neighbour, the difference being that he switched from BT whereas I had been using mobile broadband. My neighbour is also using a DG834G v3 (which I recommended as a decent cheap router) and he is also having similar issues but to a lesser degree. With his connection everything seemed fine when he was with BT with the DG834G. Could our issues be down to line training or suchlike?
I installed RouterStats on my XP partition and reconnected the DG834 and noise margin didn't go past 6db in the time I had it connected. It occasionally went down to 4db, but never higher than 6. The router didn't drop out during the short time I had RouterStats running but when I got up today there were two LCP down messages in the logs although no loss of sync, so the problem may have eased off a little. I am in the process of installing RouterStats under Wine so that I can connect the router and leave it running without switching OS.
Thanks for your help so far and I will update the thread once I have let RouterStats run with the DG for a decent period of time.
Community Veteran
Posts: 5,472
Thanks: 292
Fixes: 4
Registered: 11-08-2007

Re: Troubleshooting Psychosis: router LCP down, loss of sync

RouterStats runs perfectly in WINE on Linux, although ending the session sometimes takes longer than I would expect it to.
While you are doing that, the DG834 series can report lots of additional details to RouterStats by configuring the extended telnet settings.
The problems you have reported so far are too frequent to be line training related, much more likely to be a phone line fault.
Let RouterStats run overnight, and then see if there is any pattern to the problem, and whether your noise margin goes haywire during the hours of darkness.
Good luck.  Wink
myredhotcar
Grafter
Posts: 457
Registered: 06-11-2013

Re: Troubleshooting Psychosis: router LCP down, loss of sync

Routerstats has been running for just over 90 minutes. Oddly I have had no loss of LCP and sync in this time; everything has been running fine. I have attached a grab of the noise margin page in case it is of interest.
I have the lite version running in WINE that doesn't appear to have the Netgear telnet tab so I will leave this running as is tonight and then install the full version tomorrow.
Bizarre that it was disconnecting every few minutes initially then today with RouterStats running it is behaving. If it is line problems is it likely to be something PN can help with or will it be a BT issue, or is that a string/length kind of question?
Community Veteran
Posts: 5,472
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Registered: 11-08-2007

Re: Troubleshooting Psychosis: router LCP down, loss of sync

That looks very noisy to me !   Shocked
I suspect with that amount of noise, that it is just luck that is stopping your line from dropping sync at the moment.
Try and capture the noise margin crashing down to zero, as that will be good evidence to present to Plusnet.

I have only ever used the full RouterStats, so you are probably right about the telnet tab being missing in the 'lite' version.

Have you got your DG834 plugged into the MASTER phone socket ?, or better still the BT TEST socket ?

Do you know when will your ten day line training period will end ?

Yes, if it IS a line problem then Plusnet will be able to help, but keep doing the noise margin plots for now.

Community Veteran
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Registered: 10-06-2010

Re: Troubleshooting Psychosis: router LCP down, loss of sync

Can we get you full line stats, attenuation, speed and noise margin? It doesn't make much sense to just analyse a single value from them on its own. Although from what you've said already, it sounds like your target noise margin was increased from 6 to 9.
I use a DG834Gv3 and made my own graphing scripts. The attached graph shows what happened yesterday when the moronic DLM decided to remove interleaving from my line.
myredhotcar
Grafter
Posts: 457
Registered: 06-11-2013

Re: Troubleshooting Psychosis: router LCP down, loss of sync

After swapping splitters and cabling during the initial troubleshooting I took the bottom plate off the socket and the splitter has been plugged directly into the BT TEST socket since. If there's a wire problem I am pretty certain it is beyond that point.
As far as line training goes it is something I read about when researching the problem. PN haven't mentioned line training at all and I am merely assuming there could be line training involved. I'm fairly useless with the networking side of things and this is my first experience of this type of problem.
I will keep logging over the weekend and if anything major happens I will update this thread. I suppose I should think about potentially raising a ticket too, although I hoped to avoid that.
Thanks for your help so far Purleigh, tis much appreciated  Wink
myredhotcar
Grafter
Posts: 457
Registered: 06-11-2013

Re: Troubleshooting Psychosis: router LCP down, loss of sync

Quote from: ejs
Can we get you full line stats, attenuation, speed and noise margin? It doesn't make much sense to just analyse a single value from them on its own. Although from what you've said already, it sounds like your target noise margin was increased from 6 to 9.
I use a DG834Gv3 and made my own graphing scripts. The attached graph shows what happened yesterday when the moronic DLM decided to remove interleaving from my line.

Hi ejs do you mean the attached? If not where would I get the info you require?
EDIT: I will install the full version of RouterStats shortly. Need to get the hound out first
Community Veteran
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Registered: 15-06-2007

Re: Troubleshooting Psychosis: router LCP down, loss of sync

My guess is that it started with a default noise margin of 6dB and because of the problems it has been bounced up to 9dB which is holding sync exactly as suggested by ejs
Also the last resync at about 18.30 would have dropped the speed even more as it was after dark.so your line appears to be holding on at that setting
Note that the v3 doesn't use a Broadcom chipset unlike the v4 and the GT so isn't quite as good at hanging on. It has an AR7 chipset
Community Veteran
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Re: Troubleshooting Psychosis: router LCP down, loss of sync

It's possible that the RouterStats noise margin graph looks worse than things really are, because (by default) the AR7 chipset in the v3 reports the minimum noise margin across all the tones in use. So what appears as a huge drop on the graph could just be the margin dipping on a single tone out of the hundreds of tones in use.
It's possible to configure it to report the average margin instead, and increase the precision shown to 0.1 too. Not from the rather limited web GUI of course.
myredhotcar
Grafter
Posts: 457
Registered: 06-11-2013

Re: Troubleshooting Psychosis: router LCP down, loss of sync

Hi Oldjim
I remember reading how the v3 was inferior to some of the other models in the range, sadly a long time after I purchased it. Saying that it has performed admirably over the years for me and - for the price - has been great.
Installed the full version of RouterStats and things don't look great even to my layman eyes. I will leave it running but if the internet gets unusable with this router I will have to switch to the spare at some point (which freezes up if you throw too much data through it).
I have just noticed that the time is incorrect in my router logs (attached). Is this of relevance:
Sun, 2002-09-08 04:00:49 - Initialize LCP.
Sun, 2002-09-08 04:00:49 - LCP is allowed to come up.
Sun, 2002-09-08 04:00:54 - CHAP authentication success
Sun, 2002-09-08 04:01:04 - Send out NTP request to time-b.netgear.com
Sat, 2013-11-09 15:06:15 - Receive NTP Reply from time-b.netgear.com
Sat, 2013-11-09 15:06:55 - Administrator login successful - IP:192.168.0.2
Sat, 2013-11-09 15:05:11 - Router start up
Sat, 2013-11-09 15:38:44 - LCP down.
Sat, 2013-11-09 15:39:06 - Initialize LCP.
Sat, 2013-11-09 15:39:06 - LCP is allowed to come up.
Sat, 2013-11-09 15:39:07 - CHAP authentication success
Sat, 2013-11-09 15:39:28 - Loss of synchronization :1

Community Veteran
Posts: 5,472
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Registered: 11-08-2007

Re: Troubleshooting Psychosis: router LCP down, loss of sync

What happens to the noise margin if you reboot the DG834 now ?
Does it stay around 1dB, or does it recentre itself about 9dB ?
myredhotcar
Grafter
Posts: 457
Registered: 06-11-2013

Re: Troubleshooting Psychosis: router LCP down, loss of sync

Hi Purleigh 
This happens (at least very short term)
Community Veteran
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Registered: 11-08-2007

Re: Troubleshooting Psychosis: router LCP down, loss of sync

OK  Cry
Just let it run overnight, and we will see what it looks like in the morning !