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Author Topic: More problems with two other modems / lines  (Read 2222 times)

burakkucat

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Re: More problems with two other modems / lines
« Reply #30 on: December 17, 2018, 05:23:46 PM »

AA are looking into line 4 again.

  :(

Quote
If anyone has any advice about this line, I would be grateful. Will post up more raw stats after latest repairs if requested.

The problem is that a snapshot of the data does not provide a picture of the ongoing situation. Hence it is very difficult for those with the ability to diagnose and pronounce on a circuit.
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Weaver

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Re: More problems with two other modems / lines
« Reply #31 on: December 18, 2018, 03:38:23 AM »

Agreed. I was thinking more about matching histories.

More news. AA tell me they have switched DLM off on line 1 which was unstable at 3dB. I think from what they said they are switching off DLM on line 4, in case it is insane DLM driving speeds down and down.

I didnít even know one could switch DLM off?

They have asked me not to do a SNRM reset Ďin case doing so restarts DLMí or words to that effect. [?]
« Last Edit: December 18, 2018, 03:40:42 AM by Weaver »
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burakkucat

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Re: More problems with two other modems / lines
« Reply #32 on: December 18, 2018, 04:27:47 PM »

I didnít even know one could switch DLM off?

Yes, it is possible for ADSL2+ circuits. (My TalkTalk provided service has been so configured for many years. 6 dB target SNRM, interleaved, DLM disabled.)

Quote
They have asked me not to do a SNRM reset Ďin case doing so restarts DLMí or words to that effect. [?]

I'm not sure of the meaning of that statement. Perhaps it was a case of wanting to say something and just used the first "stream of words" that came to mind!  ::)
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Weaver

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Re: More problems with two other modems / lines
« Reply #33 on: December 19, 2018, 11:35:05 AM »

The thing is, regarding line 4, in a very recent SNRM 24-hour graph, I saw a 4dB sharp decrease in downstream noise level (upwards-going in the graph), from 4dB to 8dB vertical cliff. So I am getting far more or less noise, depending on your point of view, at times. This has not been seen before on downstream, yet this kind of step transition is very noticeable with the _upstream_on many of the lines, with either a single on/off cycle with a 24 hour period or a higher frequency cycle of several cycles per day.

So it could be that there is some equipment being switched on/off somewhere near NSBFD, in civilisation, at the exchange-end, as there is no human habitation or electrical activity anywhere near here, not even a wall or a tree for three miles upstream from this house along the cable run, and only in the last mile does one find a lot of houses.

Theory: Iím wondering if I have enjoyed my historic 3Mbps downstream sync rates while the noise is low and recently line 4 has started experiencing periods of high noise each day. If this noise extends to higher frequencies it kills the downstream performance. If it is confined to lower tones, it only affects upstream which also is on a higher 6dB margin so more resilient. And I presume thereís no DLM on upstream? But I donít know. Anyway, if I resynched during the low noise times, then at 4dB less noise, I can get my usual high sync rates, but the 4dB noise increased level is in effect at that point in the day, then I get knocked out. Presumably this confuses DLM because it canít understand whatís going on, what with the on-off noise pattern.

Thatís the best I can come up with so far.

I think it was an excellent idea from AA about turning DLM off. In my ignorance I didnít even know that that could be done with some BT lines.

I donít have any similar data for line 1, as I havenít yet installed a stats monitoring server.

I donít suppose BT will do anything about an external noise source. But given that the other lines are not getting it, surely it has to be an issue of increased _susceptibility_ in that line, no? Lack of balance perhaps? Would that make sense? Insufficient noise rejection, because of inadequate symmetry between the two sides of/conductors in that pair?
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j0hn

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Re: More problems with two other modems / lines
« Reply #34 on: December 19, 2018, 04:35:19 PM »

I donít suppose BT will do anything about an external noise source. But given that the other lines are not getting it, surely it has to be an issue of increased _susceptibility_ in that line, no? Lack of balance perhaps? Would that make sense? Insufficient noise rejection, because of inadequate symmetry between the two sides of/conductors in that pair?

Very unlikely in my opinion.
A sharp increase in SNRM of 4 dB, that comes and goes at around 4dB each time is almost certainly an item of electrical equipment running near that line.

As you say this can be anywhere between you and exchange.

Is line 4 the most recent line to be installed?
I recall AA line numbering doesn't match due to a mobile SIM.
If it is the most recent line you need to remember that line likely goes a different route to the other 3, as that line shows as coming from a PCP.

Are AA able to alter their numbering of the lines?
Can you check if this line is the line that passes through the PCP?
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Weaver

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Re: More problems with two other modems / lines
« Reply #35 on: December 19, 2018, 04:50:54 PM »

@j0hn the numbering is out of sequence as you say. No @2 is the new one, with a different D-side.

Line 4 has been in place for many years. Donít know what the story regarding the route has been. Iím not even sure that that PCP cabinet was there at all earlier, but maybe I am wrong. Iíll ask my wife if she can remember. But since I havenít been out if the house in years Iím no use.

ó

Major update. I just got Janet to swap out modems 4 and 1. Line 4 is now back up to full speed with a replacement modem. So it seems there was also something dodgy about the previous modem 4, yet again. This is not the first time I have had my suspicions, been ok for a while and then become dodgy. Iím going to put unique numbers on all of them.

Can the serial numbers be overwritten by flashing or in config or anything bad like that? I would hope not, but I just thought I had better check.

One thing is that they all seem to share the same supervisor password in my experience. Is that normal experience ? If so, then I must be simply blowing that along with the rest of the config and it is not uniquely defined by the true innate (hard) hardware.
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burakkucat

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Re: More problems with two other modems / lines
« Reply #36 on: December 19, 2018, 07:03:29 PM »

One thing is that they all seem to share the same supervisor password in my experience. Is that normal experience ? If so, then I must be simply blowing that along with the rest of the config and it is not uniquely defined by the true innate (hard) hardware.

All ZyXEL VMG1312-B10A have the same supervisor password created at power-on (cold boot) which is the documented "zyad1234". That password is then changed, later in the boot sequence, to a unique eight digit hexadecimal number (which is suspected as being related to the device serial number). [1][2]

I seem to recall you creating your own configuration for the devices and then copying (uploading) that configuration to them all. It was then that you mentioned they all shared the same supervisor password.



[1] ZyXEL VMGnnnn CPEs. Serial Number and the Supervisor Password
[2] Building and Executing MIPS executables on Intel using the crosstools
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Weaver

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Re: More problems with two other modems / lines
« Reply #37 on: December 19, 2018, 10:41:51 PM »

Thing is, I can get into all my modems with one single supervisor password.

So for some reason I am not using serial number-based passwords?

I could do with looking up the serial number of the modems for stock-keeping actually.
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burakkucat

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Re: More problems with two other modems / lines
« Reply #38 on: December 19, 2018, 10:50:07 PM »

I could do with looking up the serial number of the modems for stock-keeping actually.

In pseudo-code --

for each device; do
dumpmdm | grep -i serialnumber
done
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Weaver

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Re: More problems with two other modems / lines
« Reply #39 on: December 20, 2018, 01:05:07 AM »

Sorry for being stupid - dumpmdm needs you to be logged in as supervisor, so I had a false start until I worked that out.

But I canít seem to grep the damned thing and itís enormous. I wondered if there were perhaps no LFs in it, so I tried to use sed to insert some at sensible points, yet that didnít seem to work either.

And I canít fetch it back to the iPad either due to who knows what problem, tried writing a short program to fetch the output of dumpmdm via ssh, but all I get out of it is a goodbye message from the CLI, Ďbyeí the look of it, a cheery message in ASCII. So Iím having zero luck at the moment with everything. Iím told itís to do with old code used in their build of SSH. So really I should be querying it with telnet, and guess what, donít have the tools to do that on the iPad.

Would love to get the Raspberry Pi going some day. Wonder if I could buy an accessible one from somewhere, all set up ready to go.
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burakkucat

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Re: More problems with two other modems / lines
« Reply #40 on: December 20, 2018, 04:48:13 PM »

Does the iPad have any means of saving "whatever is happening" to a logfile?

With this computer, I open a CLI terminal and then --

[bcat tmp]$ screen -L -U ssh supervisor@AP
supervisor@ap's password:
 > dumpmdm
<many hundreds of lines>
 > exit
Connection to AP closed.

[screen is terminating]
[bcat tmp]$ grep -i serialnumber screenlog.0
      <SerialNumber>S170Y01234567</SerialNumber>
[bcat tmp]$

Other alternatives are --
  • Enter the GUI, navigate Network Map >> Status and read the third line of information.
  • Physically turn the device over and read the label on the underside.
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Westie

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Re: More problems with two other modems / lines
« Reply #41 on: December 22, 2018, 12:25:23 AM »

So really I should be querying it with telnet, and guess what, donít have the tools to do that on the iPad.

Is there a telnet tool in the "Network-Toolbox" app by Marcus Roskosch (which I think you have)?
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Weaver

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Re: More problems with two other modems / lines
« Reply #42 on: December 22, 2018, 12:48:56 AM »

Yes, there is, in fact. And I have a couple of other telnet-speaking tools.

Unfortunately I canít use the telnet protocol in Shortcuts _programs_, only SSH, which works very well normally, but with the ZyXELís implementation of SSH talking to various other kinds of software, I get weird problems.
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