Visitor

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5 Messages

Friday, September 12th, 2025

Internet Connection Dropping

I've had intermittent internet connections being dropped over my WiFi network. I finally dug into the logs for my WiFi and for my modem, and I've found that my modem had a lot of errors over the last day or two, which is corresponding to the internet going out and not coming back up within 2 minutes like it normally does. The logs show critical errors related to UCD invalid or channel unusable, SYNC timing synchronization failure, no maintenance broadcasts... things like that. My WiFi logs don't show any issues related to the WiFi network.

I was notified that Xfinity completed work in my area to fix an urgent network performance issue on Aug 21. The work didn't decrease the amount of internet connection drops, and it was really bad over the last couple of days. A tech was out the year before and mentioned that not all of the channels were "bonding" at my home... but nothing was followed up that I can tell.

Is there any way to chat with someone to take a look at either Xfinity's logs or my logs to see if there are any opportunities for a fix?

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Expert

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113.3K Messages

3 days ago

What do the modem's signal status values look like ? Try getting them here; http://192.168.100.1 or here http://10.0.0.1 

Please copy all of the text in its entirety of the *Downstream Power Levels*, the *SNR's* (Signal to Noise Ratios), and the *Upstream Power Level* numbers and paste them into your next post.


What is the exact make and model number of the modem / gateway device ?

Visitor

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5 Messages

Sure!

Here's what I was able to get: 

Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1 Locked QAM256 17 957000000 Hz -7.5 dBmV 41.4 dB 3 0
2 Locked QAM256 1 387000000 Hz -6.8 dBmV 43.0 dB 0 0
3 Locked QAM256 2 393000000 Hz -7.0 dBmV 42.9 dB 0 0
4 Locked QAM256 3 399000000 Hz -7.1 dBmV 42.8 dB 0 0
5 Locked QAM256 4 405000000 Hz -7.0 dBmV 42.9 dB 0 0
6 Locked QAM256 5 411000000 Hz -6.9 dBmV 42.9 dB 0 0
7 Locked QAM256 6 417000000 Hz -6.8 dBmV 43.0 dB 0 0
8 Locked QAM256 7 423000000 Hz -6.7 dBmV 43.0 dB 0 0
9 Locked QAM256 8 429000000 Hz -6.8 dBmV 43.0 dB 0 0
10 Locked QAM256 9 435000000 Hz -7.0 dBmV 43.0 dB 0 0
11 Locked QAM256 10 441000000 Hz -7.1 dBmV 43.0 dB 0 0
12 Locked QAM256 11 447000000 Hz -7.0 dBmV 43.0 dB 287 668
13 Locked QAM256 12 453000000 Hz -6.9 dBmV 43.0 dB 8774 37249
14 Locked QAM256 13 459000000 Hz -6.8 dBmV 43.0 dB 0 0
15 Locked QAM256 14 465000000 Hz -6.7 dBmV 43.0 dB 0 0
16 Locked QAM256 15 471000000 Hz -6.7 dBmV 43.0 dB 0 0
17 Locked QAM256 16 477000000 Hz -6.8 dBmV 42.9 dB 0 0
18 Locked QAM256 18 963000000 Hz -7.9 dBmV 41.4 dB 1 0
19 Locked QAM256 19 969000000 Hz -8.7 dBmV 41.0 dB 0 0
20 Locked QAM256 20 975000000 Hz -8.8 dBmV 41.0 dB 11 28
21 Locked QAM256 21 981000000 Hz -8.8 dBmV 40.9 dB 29 10
22 Locked QAM256 22 987000000 Hz -8.3 dBmV 41.0 dB 2 0
23 Locked QAM256 23 993000000 Hz -7.9 dBmV 41.1 dB 0 0
24 Locked QAM256 24 999000000 Hz -8.3 dBmV 40.7 dB 2 0
25 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
26 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
27 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
28 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
29 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
30 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
31 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
32 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
 
Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 2 5120 Ksym/sec 22800000 Hz 46.8 dBmV
2 Locked ATDMA 1 5120 Ksym/sec 16400000 Hz 46.3 dBmV
3 Locked ATDMA 3 5120 Ksym/sec 29200000 Hz 47.3 dBmV
4 Locked ATDMA 4 5120 Ksym/sec 35600000 Hz 47.3 dBmV
5 Not Locked Unknown 0 0 0 0.0 dBmV
6 Not Locked Unknown 0 0 0 0.0 dBmV
7 Not Locked Unknown 0 0 0 0.0 dBmV
8 Not Locked Unknown 0 0 0 0.0 dBmV
 
Downstream OFDM Channels
Channel Lock Status Profile ID Channel ID Frequency Power SNR / MER Active Subcarrier
Number Range
Unerrored
Codewords
Correctable
Codewords
Uncorrectable
Codewords
1 Locked 0 ,1 ,2 ,3 193 774000000 Hz -5.42 dBmV 41.6 dB 148 ~ 3947 1699745105 1504175419 67
2 Not Locked 0 0 0 Hz 0 dBmV 0 dB 0 ~ 4095 0 0 0
 
Upstream OFDMA Channels
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power
1 Not Locked 0 0 0 Hz 0 dBmV
2 Not Locked 0 0 0 Hz 0 dBmV

Visitor

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5 Messages

And it is a Nighthawk CM2000 running Firmware Version V8.01.02

Expert

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113.3K Messages

2 days ago

This may or may not be the root cause of the problem (YMMV) but it should be addressed regardless. 


The downstream power is on the low / weak side and it may be intermittently fluctuating even lower to out of spec levels. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.

In an effort to try to obtain better connectivity / more wiggle room, check to see if there are any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/reconfigured. Any splitters that remain should be high quality and cable rated for 5-1002 MHz, bi-directional, and no gold colored garbage from Home Depot, Target, Wal-Mart, etc. Splitters should be swapped with known to be good / new ones to test.

Also, check the coax cable for any damage such as cuts, nicks, abrasions, kinks, sharp bends, or animal chews.

If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two-way splitter connected directly off of the drop from the street / pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.


Good luck with it !

Visitor

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5 Messages

@EG​ I appreciate the response. I'm part of a complex of 4 townhouses and there may be a bit more going on here than I can check for myself. 

I've got 5 places in my home that I potentially remove/change splitters since that is where the coax cables are distributed in my townhome. I've tried moving the modem itself to all 5 different spots (over the last year) and it seems it gets better for a bit every time I move it, but within a week or so, I get the intermittent drops.

I'll get to work!

Also, I just responded to your initial post to me in this thread. If possible, could I get your opinion as to what you're seeing in the log and if I matches up with what you saw in the other data that you ask that I send? Thank you.

Expert

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113.3K Messages

2 days ago

Quite welcome ! Please redact all of the CM MAC and the CMTS MAC addresses from your error log entries for privacy. They are considered to be personal information. The posting of personally identifiable information is a violation of their forum guidelines. The forum bot will not allow your post to be seen publicly. It flagged your post as "Private".

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