Modem Power Cycles Every Hour (Sometimes Even Multiple Times Per)

Cut out again as I was posting this topic. Here's the event logs from that:

Startup Sequence

Startup Step Status Comment       Acquire Downstream Channel 603000000 Hz Locked       Upstream Connection OK Operational       Boot State OK Operational       Configuration File OK       Security Enabled BPI+

Connection Status

System Up Time 0 days 00h:03m:09s         Network Access Allowed

Downstream Bonded Channels

Channel Lock Status Modulation Channel ID Freq. (MHz) Pwr (dBmV) SNR (dB) Corrected Uncorrected    1 Locked QAM256 17 603.0 7.3 41.6 0 0    2 Locked QAM256 14 585.0 6.2 41.4 0 0    3 Locked QAM256 15 591.0 6.9 41.5 0 0    4 Locked QAM256 16 597.0 6.8 41.4 0 0    5 Locked QAM256 18 609.0 6.8 41.5 0 0    6 Locked QAM256 19 615.0 7.0 41.1 0 0    7 Locked QAM256 20 621.0 6.7 41.4 0 0    8 Locked QAM256 21 627.0 6.6 41.3 0 0    9 Locked QAM256 22 633.0 6.6 41.3 0 0    10 Locked QAM256 23 639.0 6.7 41.3 0 0    11 Locked QAM256 24 645.0 6.6 41.1 0 0    12 Locked QAM256 25 651.0 7.1 41.5 0 0    13 Locked QAM256 26 657.0 6.7 41.3 0 0    14 Locked QAM256 27 663.0 6.9 41.3 0 0    15 Locked QAM256 28 669.0 7.2 41.4 0 0    16 Locked OFDM PLC 29 780.0 7.2 40.4 2640691 0    17 Locked QAM256 30 675.0 7.1 40.9 0 0    18 Locked QAM256 31 681.0 7.6 41.3 0 0    19 Locked QAM256 32 687.0 7.5 41.4 0 0    20 Locked QAM256 33 693.0 7.9 41.5 0 0    21 Locked QAM256 34 699.0 7.8 41.4 0 0    22 Locked QAM256 35 705.0 7.9 41.4 0 0    23 Locked QAM256 36 711.0 7.7 41.4 0 0    24 Locked QAM256 37 717.0 7.8 41.3 0 0    25 Locked QAM256 38 723.0 7.5 41.3 0 0    26 Locked QAM256 39 729.0 7.9 41.3 0 0    27 Locked QAM256 40 735.0 7.7 41.1 0 0    28 Locked QAM256 41 741.0 8.0 41.2 0 0    29 Locked QAM256 42 747.0 8.1 39.9 0 0    30 Locked QAM256 43 753.0 8.1 39.4 0 0    31 Locked QAM256 44 759.0 8.1 41.2 0 0    32 Locked QAM256 45 765.0 7.8 41.0 0 0

Upstream Bonded Channels

Channel Lock Status Channel Type Channel ID Symb. Rate (Ksym/sec) Freq. (MHz) Pwr (dBmV)    1 Locked SC-QAM 69 5120 36.5 39.0    2 Locked SC-QAM 70 5120 30.1 38.8    3 Locked SC-QAM 71 5120 23.7 38.5    4 Locked SC-QAM 72 5120 17.3 38.5

Event Log

Time    Priority    Description      Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;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=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;     Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;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=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;     Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;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=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;     Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;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=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;     Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;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=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;     Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;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=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;     Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;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=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;     Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;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=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;     Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;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=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;     Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;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=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;     Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;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=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;     Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;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=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;     Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;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=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;     Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;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=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;     Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;     Time Not Established   Notice (6)   Honoring MDD; IP provisioning mode = IPv6     15:16:22 Wed May 4 2022   Notice (6)   DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;     15:16:40 Wed May 4 2022   Notice (6)   CM-STATUS message sent. Event Type Code: 24; Chan ID: 29; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0.;CM-MAC=00:00:00:00:00:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;

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@TiredOfThisISP 

O/k so even though the signal stats looked o/k at those snapshots in time, the error log entries confirm that something is going on. Perhaps there is noise ingress into the line(s) / an upstream channel / return path impairment 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 will be able to poll the CMTS (Cable Modem Termination System) to check 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 !

Thank you so much @EG. I look forward to their response.

@TiredOfThisISP 

Quite welcome !

Have you seen the response by the employee @XfinityChelseaA 13 days ago ? 

I'm going to re-escalate this.