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Intermittent connection drop

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Regular Visitor

Intermittent connection drop

Hi. I am experiencing intermittent connection drops (a few minutes a day, a few times a day) since upgrading to 1Gbps XFinity Internet (from 175Mbps) and installing a new modem (Motorola MB8600).

 

Setup is Modem (MB8600; modem only, no router) --> WiFi Router (Google Nest WiFi) --> Devices (all over WiFi; no ethernet-connected devices exist).

 

I don't have any devices that I can use to test with an Ethernet cable directly. Only one splitter between home and pole (for Cable TV and Internet).

 

Any advice would be greatly appreciated. Thank you.

 

Modem stats below.

 

Downstream:

Channel Lock Status Modulation Channel ID Freq. (MHz) Pwr (dBmV) SNR (dB) Corrected Uncorrected
   1 Locked QAM256 36 621.0 3.5 38.4 991 0
   2 Locked QAM256 17 507.0 2.1 38.4 186 76
   3 Locked QAM256 18 513.0 2.8 38.5 318 450
   4 Locked QAM256 19 519.0 3.1 38.5 358 447
   5 Locked QAM256 20 525.0 3.1 38.7 359 442
   6 Locked QAM256 21 531.0 3.2 38.7 336 510
   7 Locked QAM256 22 537.0 3.3 39.0 346 462
   8 Locked QAM256 23 543.0 3.2 38.7 363 495
   9 Locked QAM256 24 549.0 3.3 38.6 381 453
   10 Locked QAM256 25 555.0 3.3 38.5 454 498
   11 Locked QAM256 26 561.0 3.5 38.6 514 447
   12 Locked QAM256 27 567.0 3.5 38.7 496 485
   13 Locked QAM256 28 573.0 3.5 38.7 468 458
   14 Locked QAM256 29 579.0 3.7 38.8 572 465
   15 Locked QAM256 30 585.0 3.7 38.5 646 507
   16 Locked QAM256 31 591.0 3.7 38.2 929 475
   17 Locked QAM256 32 597.0 3.8 38.3 804 514
   18 Locked QAM256 33 603.0 3.9 38.1 782 480
   19 Locked QAM256 34 609.0 3.7 38.4 854 496
   20 Locked QAM256 35 615.0 3.4 38.4 978 469
   21 Locked QAM256 37 627.0 3.5 38.0 1182 474
   22 Locked QAM256 38 633.0 3.6 38.2 1119 518
   23 Locked QAM256 39 639.0 3.7 38.1 1102 455
   24 Locked QAM256 40 645.0 3.7 38.2 1132 506
   25 Locked QAM256 41 651.0 3.7 38.2 1191 458
   26 Locked QAM256 42 657.0 3.6 38.3 1257 502
   27 Locked QAM256 43 663.0 3.5 38.1 1449 436
   28 Locked QAM256 44 669.0 3.5 37.9 1337 496
   29 Locked QAM256 45 675.0 3.6 37.5 1225 464
   30 Locked QAM256 46 681.0 3.4 37.9 1295 503
   31 Locked QAM256 47 687.0 3.6 38.2 931 462
   32 Locked OFDM PLC 48 850.0 6.3 36.0 963836780 0

Power appears within band, except Channel 32?

SNR appears within band, except Channel 32?

Corrected traffic on Channel 32 seems strange?

 

Upstream:

Channel Lock Status Channel Type Channel ID Symb. Rate (Ksym/sec) Freq. (MHz) Pwr (dBmV)
   1 Locked SC-QAM 1 5120 17.3 50.0
   2 Locked SC-QAM 2 5120 23.7 49.5
   3 Locked SC-QAM 3 5120 30.3 49.3
   4 Locked SC-QAM 4 5120 36.7 48.8
   5 Locked SC-QAM 5 1280 41.2 50.3

Does power appear within band? Or high? Motorola support pages for this modem say up to 54 is within band.

 

Errors:

Time    Priority    Description 
    17:50:08
Fri May 1 2020
  Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    17:53:35
Fri May 1 2020
  Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    17:53:48
Fri May 1 2020
  Critical (3)   Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    17:54:14
Fri May 1 2020
  Critical (3)   SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    Time Not Established   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    17:59:22
Fri May 1 2020
  Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    17:59:29
Fri May 1 2020
  Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    18:02:39
Fri May 1 2020
  Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    18:02:39
Fri May 1 2020
  Critical (3)   Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    18:02:41
Fri May 1 2020
  Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    18:02:41
Fri May 1 2020
  Critical (3)   Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    18:02:42
Fri May 1 2020
  Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    18:02:42
Fri May 1 2020
  Critical (3)   Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    18:06:35
Fri May 1 2020
  Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    18:50:49
Fri May 1 2020
  Critical (3)   Resetting the cable modem due to docsDevResetNow
    Time Not Established   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    Time Not Established   Notice (6)   Honoring MDD; IP provisioning mode = IPv6
    18:52:21
Fri May 1 2020
  Notice (6)   DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    23:09:44
Sun May 3 2020
  Notice (6)   CM-STATUS message sent. Event Type Code: 20; Chan ID: 48; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    23:09:45
Sun May 3 2020
  Notice (6)   CM-STATUS message sent. Event Type Code: 22; Chan ID: 48; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    23:09:45
Sun May 3 2020
  Notice (6)   CM-STATUS message sent. Event Type Code: 23; Chan ID: 48; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    23:09:51
Sun May 3 2020
  Notice (6)   CM-STATUS message sent. Event Type Code: 24; Chan ID: 48; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0 1 2 3.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    16:48:15
Tue May 5 2020
  Notice (6)   CM-STATUS message sent. Event Type Code: 16; Chan ID: 48; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 3.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    16:48:41
Tue May 5 2020
  Notice (6)   CM-STATUS message sent. Event Type Code: 24; Chan ID: 48; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0 1 2 3.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    00:09:35
Thu May 7 2020
  Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    00:09:36
Thu May 7 2020
  Warning (5)   MDD message timeout;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    00:09:46
Thu May 7 2020
  Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    00:10:08
Thu May 7 2020
  Critical (3)   No Maintenance Broadcasts for Ranging opportunities received - T2 time-out;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    00:10:41
Thu May 7 2020
  Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    00:10:55
Thu May 7 2020
  Notice (6)   Honoring MDD; IP provisioning mode = IPv6
    00:09:58
Thu May 7 2020
  Notice (6)   DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;
    00:10:06
Thu May 7 2020
  Critical (3)   Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=XX:XX:XX:XX:XX:XX;CM-QOS=1.1;CM-VER=3.1;

 

 

Highlighted
Contributor

Re: Intermittent connection drop

Your upstream power levels are high.  I'm having very similar issues and have been unable to get a response from Comcast or through this forum.  Hopefully, you'll have better luck as the issue is likely ingress noise in the plant outside your home.

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Expert

Re: Intermittent connection drop

The upstream power is high and it may be intermittently fluctuating even higher to out of spec levels. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, and latency problems.

In a self troubleshooting effort to try to obtain better connectivity / more wiggle room, check to see if there are there 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 types like GE, RadioShack, RCA, Philips, Leviton, Magnavox, and Rocketfish from big box stores like Home Depot, Lowes, Target, Wal-Mart etc. Splitters should be swapped with known to be good / new ones to test

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.



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Regular Visitor

Re: Intermittent connection drop

Thank you for that insight. I'll let you know if Comcast does anything to address ingress noise.

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Regular Visitor

Re: Intermittent connection drop

Thanks, EG. Your diagnoses in other threads helped me understand how to read the SNR and power numbers.

 

I disconnected and re-connected the cable into the cable modem, and tightened the connection into the modem as well as (input and both outputs) at the splitter.

 

These are my new numbers on the upstream channels. Is this meaningfully better?

 

Channel Lock Status Channel Type Channel ID Symb. Rate (Ksym/sec) Freq. (MHz) Pwr (dBmV)
   1 Locked SC-QAM 1 5120 17.3 49.0
   2 Locked SC-QAM 2 5120 23.7 48.3
   3 Locked SC-QAM 3 5120 30.3 48.0
   4 Locked SC-QAM 4 5120 36.7 47.5
   5 Locked SC-QAM 5 1280 41.2 48.8

 

Also, do you have any insight into why the downstream Channel 32 is so much of an outlier (particularly the frequency, power, and corrected columns)? I note that it is using a different type of modulation (OFDM) compared to all the other downstream channels (QAM256).

 

I see a "Downstream Frequency Select" setting on the MB8600 modem. Would that be helpful in this scenario at all?

 

Thank you again.

Highlighted
Expert

Re: Intermittent connection drop


@goodsignal wrote:

Thank you for that insight. I'll let you know if Comcast does anything to address ingress noise.


Have you tried any of the suggestions ??



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Regular Visitor

Re: Intermittent connection drop

>>Have you tried any of the suggestions ??

Aah, sorry it looks like the "Reply" button doesn't quote the post I was replying to. I was responding to N0_service in my first reply. My reply after that was in response to your suggestions.

 

To clarify, there is only one splitter (originally installed by Comcast) between the street and the modem. All connections, including input/outputs at the splitter and input into the modem have been cleaned and tightened. Let me know if the numbers above are meaningfully different and/or if I can do anything else to troubleshoot before I request a tech visit from Comcast. Thank you!

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Expert

Re: Intermittent connection drop

They are a tad better but I still like to see more wiggle room. Under 45 would be preferred. It may be best to get a tech out to investigate / correct the issue. Good luck !



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