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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!
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.
Ahhh! Understood. So the codewords are some type of CRC. What do these correctable/uncorrectable codeword values normally look like? Just extremely low numbers right that indicate no noise on the line, right? Seeing that there's a similar range of errors like this across most of the channels, then I guess that could be indicative of a line/connector problem.
Lol... that's exactly what the isp said... they don't see any problems with the line when they run their tests, but after sharing some of these SYNC/No ranging response errors from the logs, they seemed a little more willing to admit to it possibly being a cable or upstream equipment issue. If it was the latter, you'd think more neighbors would be complaining though. So it must be a cable/connector. I believe the next step is begging them to come out and do a hands-on test. Thanks again for your help plemans!
plemans wrote: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.