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Millions of corrected errors on one MB8600 gigabit modem

Contributor

Millions of corrected errors on one MB8600 gigabit modem

Does anyone have any insight into this issue? Is it something to address? Can it be fixed?

 

The OFDM channel was always the last one until last week. Now it's on channel 24 and has constant errors. I've rebooted the modem several times with the same result.

 

Only thing I can see is that the SNR is low (around 15) on that channel for reasons I do not know.

 

Expert

Re: Millions of corrected errors on one MB8600 gigabit modem

It's normal. It's the nature of the beast. It's the way that the FEC (Foward Error Correction) works for that channel. All those bit errors are corrected ones. There are no uncorrected errors. They are the ones to worry about.

 

And it doesn't matter how that channel is ordered or labeled / designated. The headend technicians can configure it in any way they want to.

 

And the low SNR reading is a known firmware glitch with some makes and models of modems.

 

Are you actually experiencing any connectivity problems ?



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Contributor

Re: Millions of corrected errors on one MB8600 gigabit modem

@EG  thanks for your helpful and informative reply. No connectivity errors that I am aware of, but the bandwidth is about 100 mbps slower than before. 

 

Do the headend techs receive any notice of the errors or signal quality?  I've read elsewhere that on a DOCSIS 3.1 modem all of the signal-to-noise numbers should be > 36 and that < 33 will cause problems.  (The SNR today is 14.9 on the OFDM PLC locked channel 24)

 

https://pickmymodem.com/signal-levels-docsis-3-03-1-cable-modem/

 

We added a separate eMTA for Comcast voice services and are using a -3.5 dB splitter.

Could the splitter or additional cable modem have anything to do with it?

 

 

New Poster

Re: Millions of corrected errors on one MB8600 gigabit modem

I am having this exact issue. SNR is about 16.3 on OFDM PLC channel, and I only noticed this after an apparent firmware upgrade to my modem, prior to that it was fine. Over 10 days there were about 700million correctables. Zero uncorrectables. NO correctables on any other channel.

Contributor

Re: Millions of corrected errors on one MB8600 gigabit modem

@foxmanb did your OFDM PLC channel change? Mine used to be the last one (32) with no errors and now it is 24. The OFDM PLC chnnel SNR is usually around 15 with a power level hovering near 0 while the rest of channels have SNR's of about 30-45 with power levels between about 2 and 6. No errors on them, and no unorrected errors but many billions of corrected errors now.

New Poster

Re: Millions of corrected errors on one MB8600 gigabit modem

I don't believe the channel assignment changed, it was just that I noticed the firmware had changed based on the modem not logging me out every 20 min, I keep a pretty good eye on my connection, that's when I noticed the horrible SNR on the OFDM PLC channel.

Prior ot the firmware upgrade, my SNR's on all channels were between 38 and 42, power levels aroun 1-3dBmV, after the firmware upgrade, every channel is the same except for the ODFM PLC channel which has a horrible SNR and tons of correctable errors. I have no correctables on any other channel.

 

Comcast has also disabled the signal analyzer in our modems, so I can't use that to help figure out what's going on.

New Poster

Re: Millions of corrected errors on one MB8600 gigabit modem

This is from 8 days w/o a reboot.

  Downstream Bonded Channels

Channel Lock Status Modulation Channel ID Freq. (MHz) Pwr (dBmV) SNR (d Corrected Uncorrected
1 Locked QAM256 31 645.0 1.5 41.6 0 0
2 Locked QAM256 1 453.0 0.5 41.7 0 0
3 Locked QAM256 2 459.0 0.8 42.0 0 0
4 Locked QAM256 3 465.0 0.8 41.8 0 0
5 Locked QAM256 4 471.0 0.7 41.8 0 0
6 Locked QAM256 5 477.0 0.8 41.8 0 0
7 Locked QAM256 6 483.0 0.9 41.7 0 0
8 Locked QAM256 7 489.0 0.7 41.8 0 0
9 Locked QAM256 8 495.0 0.7 41.3 0 0
10 Locked QAM256 9 519.0 0.1 38.5 0 0
11 Locked QAM256 10 525.0 -0.3 41.3 0 0
12 Locked QAM256 11 531.0 -0.7 41.3 0 0
13 Locked QAM256 12 537.0 -0.8 41.2 0 0
14 Locked QAM256 13 543.0 -1.0 41.0 0 0
15 Locked QAM256 14 549.0 -0.8 41.2 0 0
16 Locked QAM256 15 555.0 -0.6 41.1 0 0
17 Locked QAM256 16 561.0 -0.4 41.2 0 0
18 Locked QAM256 17 567.0 -0.1 40.1 0 0
19 Locked QAM256 18 573.0 0.3 41.3 0 0
20 Locked QAM256 19 579.0 0.3 41.4 0 0
21 Locked QAM256 20 585.0 0.5 41.2 0 0
22 Locked QAM256 21 591.0 1.3 41.6 0 0
23 Locked QAM256 22 597.0 1.3 41.5 0 0
24 Locked QAM256 23 603.0 0.8 41.3 0 0
25 Locked QAM256 24 609.0 1.0 41.3 0 0
26 Locked QAM256 25 615.0 0.9 40.6 0 0
27 Locked QAM256 26 621.0 0.7 41.3 0 0
28 Locked QAM256 27 627.0 1.4 41.6 0 0
29 Locked QAM256 28 633.0 1.9 41.5 0 0
30 Locked OFDM PLC 29 690.0 4.9 16.3 616441119 0
31 Locked QAM256 30 639.0 1.3 41.5 0 0
32 Locked QAM256 32 651.0 1.9 41.7 0 0

Contributor

Re: Millions of corrected errors on one MB8600 gigabit modem


@foxmanb wrote:

I don't believe the channel assignment changed, it was just that I noticed the firmware had changed based on the modem not logging me out every 20 min, I keep a pretty good eye on my connection, that's when I noticed the horrible SNR on the OFDM PLC channel.

Prior ot the firmware upgrade, my SNR's on all channels were between 38 and 42, power levels aroun 1-3dBmV, after the firmware upgrade, every channel is the same except for the ODFM PLC channel which has a horrible SNR and tons of correctable errors. I have no correctables on any other channel.

 

Comcast has also disabled the signal analyzer in our modems, so I can't use that to help figure out what's going on.


Almost identical situation here. They want to send a tech, but I think that will be a waste of time....

 

Expert

Re: Millions of corrected errors on one MB8600 gigabit modem


@foxmanb wrote:

that's when I noticed the horrible SNR on the OFDM PLC channel.

Prior ot the firmware upgrade, my SNR's on all channels were between 38 and 42, power levels aroun 1-3dBmV, after the firmware upgrade, every channel is the same except for the ODFM PLC channel which has a horrible SNR and tons of correctable errors. I have no correctables on any other channel.


Have you seen my earlier post about that ?



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New Poster

Re: Millions of corrected errors on one MB8600 gigabit modem

Yep, saw the earlier post, a search led me to it.

 

To muddy the waters further. I took my modem to a friends house a couple blocks away today... On his Netgear, OFDM PLC was reading fine... Connected my modem, it synced right up, but still had the low reading on the OFDM PLC channel Smiley Sad.

Contributor

Re: Millions of corrected errors on one MB8600 gigabit modem

FYI, and similar to what @EG  commented, there appears to be a Comcast issue with the particular gigabit modem I am using (MB8600). Talking to Logan at Motorola, I learned the following.   I don't know how large a number the modem will record but so far it's about 450 billion and growing. 

 

 

Logan P. (Motorola Mentor)

May 23, 12:59 PM EDT

Hello,

The ISP is not reporting the channels properly. We are working with their engineers to fix that but as there is no issues caused by it there is no ETA.

Regards,

Technical Support Services
Motorola Cable LLC
1-800-753-0797
M-F 8:30 AM - 10:00 PM ET

Expert

Re: Millions of corrected errors on one MB8600 gigabit modem

Thank you for sharing that info !



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