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Forum Discussion
G0atHax0r
May 14, 2020Aspirant
CM1000 intermittent connection loss on XFinity cable
Hi All, I'm troubleshooting what seems to be intermittent drops throughout the day on XFinity cable... and the culprit is either the CM1000 going bad, or some kind of line quality/hardware issues...
- May 29, 2020
So here's an update to my situation... it seems that Googalabosh was experiencing similar issues, so I'll write down my findings/experience here...
1.) XFinity tech came out and ran tests from the entry point to my CM1000 cable modem - no problems (and no, there are no splitters... it's a straigh run)
2.) XFinity tech ran a test from the entry point to the junction box at the street - no problem.
3.) XFinity tech ran a test from the junction box at the street, to the nearest node - again, no problems...
He said everything according to his readings were within parameters and nothing looked abnormal. This was frustrating both to me and him, since we couldn't pinpoint anything weird. I asked him if he could put a network monitor on our account, which he was happy to do -- and I would *recommend* you asking for this same thing. This will give them detailed reports of when things misbehave, which is what I suspect happened in my case.
After the tech left, my device continued to drop for the next few days off and on throughout the day... then, things stabilized. My connection has not dropped for almost 4 days straight now., which is unheard of. :) The tech said he or someone else would call back and give an update, but I have not heard anything yet. I will definitely find out what the problem was, but I suspect it had to do with some changes at the upstream node.
I started keeping careful track of what my modem stats were looking like throughout the day, and found that if the downstream channels power dropped below -4.5 or -5 dBmV, which also seems to drop the SNR/MER to below 36dB, then I would start accumulating more and more uncorrectable codewords, including drops. Since they did something on their end, my power has remained around -2 or -3dBmV and the SNR/MER remains at 40dB on average...
I would focus on ensuring that these values are in the middle of the range (Power should ideally be at 0dBmV and SNR/MER should ideally be at 40dB), but it fluctuates up or down... which typically is still OK, but I guess certain modems/connections are more finicky than others. Hope this helps!
plemans
May 17, 2020Guru - Experienced User
do you also have the Cable connection page to go with the logs?
- G0atHax0rMay 18, 2020Aspirant
plemans wrote:
do you also have the Cable connection page to go with the logs?Unfortunately I don't have a snapshot of these connection logs when the issue is occurring, but I'll try for next time. Here's what they look like when things are working:
Frequency start Value This field below allows you to modify the frequency the cable modem start with its scan during initialization and registration. Enter the new start frequency and restart the cable modem for it to take effect. Starting Frequency <tabindex=-1>Startup Procedure</tabindex=-1>
Procedure Status Comment Acquire Downstream Channel 579000000 Hz Locked Connectivity State OK Operational Boot State OK Operational Security Enable BPI+ IP Provisioning Mode Honor MDD IPv6 only <tabindex=-1>Downstream Bonded Channels</tabindex=-1>
Channel Lock Status Modulation Channel ID Frequency Power SNR / MER Unerrored Codewords Correctable Codewords Uncorrectable Codewords 1 Locked QAM256 17 579000000 Hz -2.7 dBmV 39.6 dB 46209713 14779 14713 2 Locked QAM256 1 483000000 Hz -3.1 dBmV 39.1 dB 45233431 370 70 3 Locked QAM256 2 489000000 Hz -2.9 dBmV 39.2 dB 64685880 5903 28809 4 Locked QAM256 3 495000000 Hz -2.8 dBmV 39.6 dB 64692870 5652 27540 5 Locked QAM256 4 501000000 Hz -3.0 dBmV 39.3 dB 64697151 5531 26572 6 Locked QAM256 5 507000000 Hz -2.8 dBmV 39.4 dB 64700840 3120 14280 7 Locked QAM256 6 513000000 Hz -2.6 dBmV 39.6 dB 64706758 5173 24780 8 Locked QAM256 7 519000000 Hz -2.9 dBmV 39.3 dB 64711093 1930 7965 9 Locked QAM256 8 525000000 Hz -3.3 dBmV 39.1 dB 64720231 1325 4830 10 Locked QAM256 9 531000000 Hz -3.1 dBmV 39.3 dB 64724479 5480 26491 11 Locked QAM256 10 537000000 Hz -3.0 dBmV 39.4 dB 64723792 5836 27966 12 Locked QAM256 11 543000000 Hz -3.1 dBmV 39.3 dB 64729815 5170 24677 13 Locked QAM256 12 549000000 Hz -2.9 dBmV 39.4 dB 64735703 782 1044 14 Locked QAM256 13 555000000 Hz -2.6 dBmV 39.6 dB 64739574 5608 27443 15 Locked QAM256 14 561000000 Hz -2.7 dBmV 39.3 dB 64742700 5930 28637 16 Locked QAM256 15 567000000 Hz -2.9 dBmV 39.4 dB 64745371 5661 27281 17 Locked QAM256 16 573000000 Hz -2.7 dBmV 39.5 dB 64769644 9418 25081 18 Locked QAM256 18 585000000 Hz -2.8 dBmV 39.5 dB 64774172 17178 15246 19 Locked QAM256 19 591000000 Hz -2.7 dBmV 39.5 dB 64783828 22025 5417 20 Locked QAM256 20 597000000 Hz -2.3 dBmV 39.6 dB 64794547 18760 2065 21 Locked QAM256 21 603000000 Hz -2.4 dBmV 39.5 dB 64793880 21515 4126 22 Locked QAM256 22 609000000 Hz -2.3 dBmV 39.5 dB 64798198 21891 3794 23 Locked QAM256 23 615000000 Hz -1.8 dBmV 39.8 dB 64808961 15205 1087 24 Locked QAM256 29 459000000 Hz -2.8 dBmV 39.4 dB 64797187 5564 27605 25 Locked QAM256 34 465000000 Hz -2.8 dBmV 39.3 dB 64798205 5915 28846 26 Locked QAM256 35 471000000 Hz -2.7 dBmV 39.4 dB 64792486 5790 27849 27 Locked QAM256 36 477000000 Hz -3.0 dBmV 39.1 dB 64794992 5871 28804 28 Locked QAM256 38 429000000 Hz -2.3 dBmV 39.4 dB 64767490 5246 25934 29 Locked QAM256 39 435000000 Hz -2.8 dBmV 39.1 dB 64779295 423 514 30 Locked QAM256 40 441000000 Hz -3.1 dBmV 39.1 dB 64774997 920 2066 31 Locked QAM256 41 453000000 Hz -2.6 dBmV 39.5 dB 64777052 5852 28958 32 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0 0 <tabindex=-1>Upstream Bonded Channels</tabindex=-1>
Channel Lock Status Modulation Channel ID Frequency Power 1 Locked ATDMA 1 35800000 Hz 47.0 dBmV 2 Locked ATDMA 2 29400000 Hz 46.8 dBmV 3 Locked ATDMA 3 23000000 Hz 46.5 dBmV 4 Not Locked Unknown 0 0 Hz 0.0 dBmV 5 Not Locked Unknown 0 0 Hz 0.0 dBmV 6 Not Locked Unknown 0 0 Hz 0.0 dBmV 7 Not Locked Unknown 0 0 Hz 0.0 dBmV 8 Not Locked Unknown 0 0 Hz 0.0 dBmV <tabindex=-1>Downstream OFDM Channels</tabindex=-1>
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power SNR / MER Active Subcarrier Number Range Unerrored Codewords Correctable Codewords Uncorrectable Codewords 1 Locked 0, 1, 2, 3 37 690000000 Hz 0.4 dBmV 32.0 dB 1228 ~ 2867 298986550 236769966 17558813 2 Not Locked 0 0 0 Hz 0.0 dBmV 0.0 dB 0 ~ 4095 0 0 0 <tabindex=-1>Upstream OFDMA Channels</tabindex=-1>
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power 1 Not Locked Unknown 0 0 Hz 0 dBmV 2 Not Locked Unknown 0 0 Hz 0 dBmV Current System Time: Sun May 17 19:54:51 2020System Up Time: 26:39:57
- plemansMay 18, 2020Guru - Experienced User
You have a bunch of errors in your line. Not a few, a bunch.
If you don't have any splitters, attenuators, amplifiers, or extended runs, then your isp needs to check the line.
goal is to connect right where the coax enters the home to prevent the isp from saying the issues is the wiring within the home.
- G0atHax0rMay 18, 2020Aspirant
plemans wrote:You have a bunch of errors in your line. Not a few, a bunch.
If you don't have any splitters, attenuators, amplifiers, or extended runs, then your isp needs to check the line.
goal is to connect right where the coax enters the home to prevent the isp from saying the issues is the wiring within the home.
I appreciate your feedback, plemans! Could you please share some more specific information? I'm assuming you're talking about these sample errors that keep repeating below, right? I'm pretty decent at deciphering windows server errors and whatnot, but cable modem/communication-specific errors are not my expertise. What typically are the cause for these kinds of errors, and what should I be looking out for? For instance, could this be an physical cable problem? If so, why would it only happen intermittently? Could it be the CM1000 flaking out? Why or why not? Would I see different errors? Is it an upstream hardware issue not producing enough voltage, or not supplying what's necessary to maintain a sync connection, or timing hardware failures?
2020-05-14, 10:41:35 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1; 2020-05-14, 10:41:29 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1; 2020-05-14, 10:41:28 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
I don't have any splitters, attenuators, amplifiers or extended runs. I appreciate your help! :)