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Saturday, June 15th, 2024 2:56 PM

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Modem requires restarting every day

I have an 800Mbps plan. When everything's right, I get that speed all the way to devices. Unfortunately it frequently degrades to 50-150Mbps even on devices hard-wired to the router. Power-cycling the modem resolves the issue, but having to do this daily (or live with the degraded speeds) is frustrating.

I've tried replacing the modem. Was using Hitron CODA56 Multi-Gigabit DOCSIS 3.1 Modem but replaced it with ARRIS SURFboard SB8200 DOCSIS 3.1 Cable Modem. This appeared to make no difference. I still have to power cycle it frequently.

Whenever I've called Xfinity, they've had me power cycle it and then suggested the issue was resolved. Of course, this does resolve the issue but only temporarily.

Any ideas on what I could try to troubleshoot?

Accepted Solution

Expert

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110.1K Messages

11 months ago

No worries, and you're quite welcome ! Ok so there is a problem with the SNR values on downstream channels 26 to 32. They are all too low / out of spec. And there are a large number of uncorrected bit errors as well. It seems that there is spurious noise leaking into the line(s) somewhere at that range of frequencies. 

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 connection quality, check to see if there are any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. 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, etc.

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 !

(edited)

Expert

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110.1K Messages

11 months ago

What do the modem's signal stats look like ? Try getting them here; http://192.168.100.1 

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.

Expert

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110.1K Messages

11 months ago

Please redact the CM MAC and the CMTS MAC address from that error log entry for your privacy. It is 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".

5 Messages

My bad. Let's try this again. Hey @EG -- appreciate your help! Here's what I can find. I don't see anything on SNR in the web GUI.

Downstream Bonded Channels
Channel ID Lock Status Modulation Frequency Power SNR/MER Corrected Uncorrectables
20 Locked QAM256 507000000 Hz 2 dBmV 41 dB 0 0
17 Locked QAM256 483000000 Hz 3 dBmV 41 dB 0 0
18 Locked QAM256 489000000 Hz 2 dBmV 41 dB 0 0
19 Locked QAM256 495000000 Hz 2 dBmV 40 dB 0 0
21 Locked QAM256 513000000 Hz 2 dBmV 40 dB 0 0
22 Locked QAM256 519000000 Hz 2 dBmV 41 dB 0 0
23 Locked QAM256 525000000 Hz 1 dBmV 41 dB 0 0
24 Locked QAM256 531000000 Hz 1 dBmV 41 dB 0 0
25 Locked QAM256 543000000 Hz 1 dBmV 41 dB 0 0
26 Locked QAM256 549000000 Hz 1 dBmV 36 dB 0 0
27 Locked QAM256 555000000 Hz 1 dBmV 27 dB 73667156 8482863
28 Locked QAM256 561000000 Hz 1 dBmV 0 dB 241752219 161635766
29 Locked QAM256 567000000 Hz 1 dBmV 31 dB 0 0
30 Locked QAM256 573000000 Hz 1 dBmV 29 dB 72107 11
31 Locked QAM256 579000000 Hz 1 dBmV 27 dB 4673408 8981
32 Locked QAM256 585000000 Hz 1 dBmV 32 dB 0 0
33 Locked QAM256 591000000 Hz 0 dBmV 37 dB 0 0
34 Locked QAM256 597000000 Hz 1 dBmV 39 dB 0 0
35 Locked QAM256 603000000 Hz 0 dBmV 40 dB 0 0
36 Locked QAM256 609000000 Hz 0 dBmV 40 dB 0 0
37 Locked QAM256 615000000 Hz 0 dBmV 40 dB 0 0
38 Locked QAM256 621000000 Hz 0 dBmV 39 dB 0 0
39 Locked QAM256 627000000 Hz 0 dBmV 38 dB 0 0
40 Locked QAM256 633000000 Hz 0 dBmV 39 dB 0 0
41 Locked QAM256 639000000 Hz 0 dBmV 40 dB 0 0
42 Locked QAM256 645000000 Hz 0 dBmV 40 dB 0 0
43 Locked QAM256 651000000 Hz 0 dBmV 40 dB 0 0
44 Locked QAM256 657000000 Hz 0 dBmV 40 dB 0 0
45 Locked QAM256 663000000 Hz -1 dBmV 40 dB 0 0
46 Locked QAM256 669000000 Hz -1 dBmV 40 dB 0 0
47 Locked QAM256 675000000 Hz -1 dBmV 39 dB 0 0
48 Locked OFDM PLC 688000000 Hz -1 dBmV 37 dB 131255439 9967


Upstream Bonded Channels
Channel ID Lock Status US Channel Type Frequency Width Power
1 Locked SC-QAM 16400000 Hz 6400000 42.0 dBmV
2 Locked SC-QAM 22800000 Hz 6400000 43.0 dBmV
3 Locked SC-QAM 29200000 Hz 6400000 43.8 dBmV
4 Locked SC-QAM 35600000 Hz 6400000 44.3 dBmV

I also notice a lot of messages like these in the event log--not sure if that's related:

MDD message timeout;CM-MAC=...;CMTS-MAC=...;CM-QOS=1.1;CM-VER=3.1;

5 Messages

11 months ago

Thanks again, @EG. Good to have some sense of the problem. I've tried the steps suggested above. There are actually no splitters at all, but there are two connectors between the street and my modem that I took off, cleaned, and replaced. If anything it appears to have exacerbated the problem (see below). I guess I could try replacing them but they seem in fine condition.

5 Locked QAM256 543000000 Hz 1 dBmV 40 dB 0 0
26 Locked QAM256 549000000 Hz 0 dBmV 33 dB 0 0
27 Not Locked Unknown 555000000 Hz 0 dBmV 0 dB 1990 0
28 Not Locked QAM256 561000000 Hz 0 dBmV 0 dB 26633 0
29 Locked QAM256 567000000 Hz 0 dBmV 28 dB 61007 0
30 Locked QAM256 573000000 Hz 0 dBmV 35 dB 0 0
31 Locked QAM256 579000000 Hz 0 dBmV 30 dB 0 0
32 Locked QAM256 585000000 Hz 0 dBmV 30 dB 0 0
33 Locked QAM256 591000000 Hz 0 dBmV 36 dB 0 0
34 Locked QAM256 597000000 Hz 0 dBmV 40 dB 0 0

I tried to get help through the Xfinity assistant but it detected no issues with the modem and then suggested the problem was unrelated to Xfinity service. I guess I didn't guess the magic path to get a technician. I can't even find a way to speak to a person. A bit frustrating, but I'll keep trying.

Expert

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110.1K Messages

11 months ago

If there is nothing more that can be done to improve the connection quality, then you'll need a tech visit as stated. 


Bear in mind that if the premises facing techs can not find or fix a problem at your home, it is they who are responsible for escalating it up to their line / network / maintenance dept. techs. The problem may lie beyond your home in the local neighborhood infrastructure somewhere but it is their S.O.P. to start at the home. And if the problem is found to be on their side of the demarcation point, there will not be any charge.


Good luck !

5 Messages

I was able to get a tech visit scheduled. Before he arrived, I had taken the modem and router outside to test them when connected directly to the coax from the street. I found the SNR was fine when they were connected directly there so knew the issue was between that cable and my house. I told the technician this. He was a little dubious, said it's typically a modem issue. But he replaced this filter and, sure enough, the SNR was resolved with everything connected in the house. It was a 8-10am service window. He arrived at 7:45am and was done by 7:55am. Lovely guy, too.

Big thank you to @EG for showing and explaining to me the issue in the modem status! That really allowed me to troubleshoot properly and also saved the tech a lot of time.

Expert

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110.1K Messages

11 months ago

You're very welcome @shane0  ! Glad you got it squared away !! Now closing your solved topic.

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