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Topic # 112057 24-Nov-2012 17:45 Send private message

So I have a customer who has VDSL from Kiwilink. It is just a standard VDSL connection with POTS. Customer is less than 200m from the cabinet and gets very good sync rates (52/10 on 8b) The house was re-cabled (by me) about 2 years ago with Cat 6 - including to the demarc. 2-pair underground lead comes to the ETP and is joined directly to the Cat 6 that goes to the patch panel upstairs. In the panel is a VDSL splitter and a dedicated jack for the modem to be plugged in to. Modem is a Zyxel P870 and is the main router for the network. Nothing special about the network. There is an unmanaged 24-port GigE switch, couple of WAP's and an asterisk server. There are a couple of IP phones and then about 5 computers (laptops and desktops) and a handful of smart phones.

Fault is the connection is dropping every couple of days. They don' get the net back until the modem is reset.

I have replaces the modem once. Changed the splitter for another one. Changed line cords. used different pairs in the cat 6 feeder cable.

Now we have finally got Chorus to come and have a look as it was the only thing not ruled out. I had already used a dynatel on the line though and got what I thought were good results.

So Mr. Chorus (a fault man who I know to be very good at what he does) came and used his dynatel and got very good results on the pair to the cabinet (right up to 90dB of longitudinal balance).

He then suspected the power level was too high as the customer is so close. Rang the data guys and they informed him that DLM is off and settings were being done manually (I knew this as this is what Kiwilink had told us Chorus were doing to monitor it). So the data guys turned DLM back on  hoping it would adjust things to suit the line and are monitoring the line for 7 days as of Friday. Cutomer text me this afternoon saying that it dropped out again today. Oh and they had manually set it to use the 17a profile so gets a sync rate of around 61/11 with around 5dB of attenuation.

I am just totally out of ideas to fix this. It is fairly important his connection stays up as VoIP is his main means of communication. Obviously we have fail over to cell in place but it just shouldn't be an issue.

Can anyone think of anything???!

One last thought I had was bringing the modem out of the panel and terminating the DSL right at the demarc then sending ethernet up to the patch panel. I just don't think it would make that much of a difference considering it is Cat 6 cable.

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  Reply # 723583 27-Nov-2012 12:47 Send private message

No one has any other ideas?

Heard back from the fault man today. He said the modem had been 'turned off' over night and came up at 4.30am. I rang the customer and, as expected, he had not turned the modem off as he is on call at night being a doctor so can't miss any calls. I am having trouble deciding on how they know the difference between a modem being off and not synced up.

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  Reply # 723597 27-Nov-2012 13:07 Send private message

They probably can't tell.

I assume you've rechecked all the internal cabling.

Seems like a line fault, affected by temperature / rain / lunar alignment -ie an iffy joint somewhere or bad cable.

Get ISP/Chorus to check all the joints and cabling between the house and exchange to make sure they're sound.  GL, these very transient issues can be difficult to get resolved.



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  Reply # 723786 27-Nov-2012 18:40 Send private message

Checked internal cabling. There are two Cat 6 to the demarc and have run the connection over both with no difference.

It looks like a line fault but the Dynatel says the line is very very good. There is only one joint between the customer and the cabinet and that is in the BDD pit right outside the customers house.

I wonder if that solar eclipse had anything to do with it lol...

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  Reply # 723795 27-Nov-2012 18:53 Send private message

When you say you changed the modems, did you use the same model/brand (Zyxel) both times? Maybe try a different model\brand if possible?

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  Reply # 723818 27-Nov-2012 19:48 Send private message

Have you had kiwilink run a 7 day monitor on the line in sqm?  That should help give you an idea what's going on.  If you get hold of someone really good they may be able to run it directly on the 5530NA which gives a whole lot more useful information on the line from the ISAM.

Plus have you tried different devices such as the fritz!box (which Snap sell) are pretty good (not that I have tried one but have heard good reviews)




I work for Spark, but as always my views are my own.



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  Reply # 723901 27-Nov-2012 22:48 Send private message

Yes I replaced it with another Zyxel. I have pretty much exclusively used Zyxel's for VDSL installs and have no problems at other sites (albeit not that many but still enough to say they are decent). In fact this doctor has VDSL at his surgery too with the same modem and it has absolutely no issues. I have a Fritzbox! that could be worth a go - will try that after this 7 day period. Just don't think the probability of 2 faulty modems is that high at all.

They (Chorus) are running a 7 day test at the moment. Whether that is the test you are talking about I'm not sure. Will get on to Kiwilink and see if that one has been done.

So is it possible to tell the difference between the modem being off and just not synced up?

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  Reply # 723911 27-Nov-2012 23:25 Send private message

chevrolux: Just don't think the probability of 2 faulty modems is that high at all.


Practically zero I'd guess, but perhaps not faulty per se,  maybe just something odd going on... Like I seem to remember reading somewhere that some ADSL2 modems (Vigor?) couldn't sync with specific DSLAMs - maybe you've found a similar bug with the Zyxel that manifests in a different way?

I'm no experet so have no idea if anything like this is even possible, but it sounds like you've looked at everything else so if the 7 day test chorus are running brings up nothing then maybe tossing the fritzbox at it would be worth a shot.

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  Reply # 723915 27-Nov-2012 23:33 Send private message

Well as someone who has put in around 10 Zyxel Modems for VDSL (and hundreds for ADSL) I'd say the chances of a faulty Zyxel let alone two are very unlikely. It's a very strange sounding fault for sure. Hopefully the Line test will find something.


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  Reply # 723953 28-Nov-2012 06:59 Send private message

I think you need to try a different router - sounds like modem and line card don't like each other. I know with the Cisco VDSL routers there is a pile of custom firmware loads to resolve various comparability issues with DSLAMs

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  Reply # 723967 28-Nov-2012 08:01 Send private message

I too would try a different modem. I've installed a lot of Zyxel's for VDSL2 now and have seen the odd strange issue with them. Swapping the modem is the only way to emilinate it as the cause.

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  Reply # 725349 30-Nov-2012 23:53 Send private message

If a different modem doesn't fix it then push the ISP to get the port at the cabinet changed. Having said that, you could also try adding some attenuation to the line as some modems struggle to hold sync when the loop is too short




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  Reply # 725517 1-Dec-2012 14:57 Send private message

Well the 7 day period finished on friday and showed there had been 3 re-syncs in that period. The faultman has changed the port and is doing another 7 days. I haven't put a different modem in yet as i just want to have one thing change at a time. If this doesn't fix it I will put a fritzbox in.



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  Reply # 730672 11-Dec-2012 17:30 Send private message

Well it's nearly been two weeks and I have had no emails from the customer about drop outs!!!

So looks like the fix was change port and put DLM back on. Thanks Chorus!! So so glad to have this sorted.

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  Reply # 730771 11-Dec-2012 19:44 Send private message

Glad it wasn't a modem :)

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