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Frequent disconnects since DOCSIS 3.1 modem
Upgraded to gigabit a few months back but was on an older modem that wasn't capable of gigabit. Waited about a month to buy the new modem. Zero connection issues in this time. The moment I installed my new MB8600, I started getting internet disconnects at least once a day that went away immediately with a power cycle. I thought the momem was faulty so I replaced with another MB8600; same issue. Just replaced that one with the new MB8611 and issue still persists. Comcast was out yesterday checking my line, saying it looked fine (only plugged in their device to check signal levels and packet loss, etc.). OFDM Modulation has a ton of corrections but I understand that to be a bug. A friend said he had the exact issue and wasn't resolved until he insisted that Comcast replace the lines. Is that likely the case?
EG
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110.6K Messages
4 years ago
The signal stat values are o/k / in spec. The OFDM downstream channels have no uncorrected errors, so that's not an issue.
So, even though the signal stats looked o/k at that snapshot in time, the error log entries confirm that something is going on. Perhaps there is noise ingress into the line(s) somewhere.
There are other signal stat figures that can't be read by the modem. They are the "Upstream Rx Power" (Upstream Receive Power Level), the "Upstream SNR Ch." (Upstream Signal To Noise Ratio), and the "Upstream ICFR" (In Channel Frequency Response). These are as equally important in diagnosing connectivity issues as are the modem's stats.
I'm going to escalate your issue to the Comcast corporate employees that are available to these boards. They can check the CMTS (Cable Modem Termination System) for any real time degradation and / or error reports, see your node / cable plant and modem health, and see whether or not everything is in the green zone. They can also see a history plot for the modem and poll for those upstream receive signal stats.
You should get a reply here in your topic. Good luck !
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E-Squared
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4 years ago
For what it's worth, I found this post helpful as I was having a very similar issue and found this thread by searching with the string from one of the log entries generated by my MB8611. I was getting frequent disconnects, randomly a few times a day.
I appear to have fixed it by disconnecting the input coax cable to the modem, then cleaning the center copper wire with a q-tip dipped in isopropanol. I saw visible corrosion on the q-tip (small black residue.) Then carefully reconnected the cable, made sure the center wire was seated as far in as possible and I tightened up the nut with the wrench that came with the modem. It's been up for three days now with no entries in the log, no disconnects.
The cable in question was quite new, installed by Xfinity techs in 2019. The house is a new build as well. The cable was connected to my old modem until last week when I updated the modem. Everything is contained in a network box inside the house.
It appears that as the technology advances that allows them to jam more and more frequencies on ancient coax cable, everything needs to be absolutely perfect for each physical connection. Very much looking forward to the fiber they just ran to my house to get lit up!
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