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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...
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!
do you also have the Cable connection page to go with the logs?
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. | |
|
<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
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.
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! :)
I'm talking your codewords. Some are correctable and some aren't. Tie those in together with your logs and there's usually line issues causing it.
It could be damage to a coax line, bends, wear, or even moisture in the line. It could be corrosion to a connector. it could be a poorly installed connector. it could be an issues at the box. Its tough to say exactly.
but if you have the modem directly connected to where the coax is entering the home and you're still getting those, your isp needs to check the line.
It always potentially can be a modem. connectors/hardware does go bad sometimes.
And sometimes the isp will say "our lines fine, its your 3rd party modem". I've had to rent an ISP modem for a month to prove it wasn't the modem so they'd fix a line before. Problem with that is that some isp's are locking down their modem page so the home user can't even check anymore.