My modem log shows repeated kernel-panic reboots, SYNC Timing Synchronization failures, and T3 timeouts, all indicating a clear problem with upstream/downstream signal quality on the line or at the node. The modem frequently loses its DOCSIS 3.1 lock and falls back to DOCSIS 3.0, which also explains the reduced speeds.This is not a LAN issue. These are network-level signal faults.I kindly request an on-site technician visit with full signal measurement ( SNR, downstream/upstream power, OFDM stability, outdoor connectors, and tap/not check).Please escalate this issue, as it is persistent and severely impacting service reliability.

Look at the last entry in the log you posted. We can all see the kernel panic message. This is a defective Hub.

Can you post a more complete log (as text)? The events just after a crash/reboot are somewhat meaningless.

Intel Atom CPU Kernel Panic Restarts are a fault of the Intel CPU in the VM Hub.The only fix is to request a replacement VM Hub.If you have DOCSIS signal level concerns, share the contents of the Upstream and Downstream status tabs for review.

This is the 2nd hub I got within a year. I don't think is the issue.

If the modem were defective, it would not display SYNC Timing Synchronization failures, T3 timeouts, DS profile reassignments or OFDM instability before rebooting. These specific events indicate clear network-side signal issues rather than a hardware fault. The kernel panic is a secondary reaction to these failures, not the root cause.I am absolutely fine with replacing the modem if necessary, but please escalate this case for a full line and node-level signal check, because the logs clearly point to upstream/downstream timing instability.A faulty modem does not produce upstream ranging timeouts, as those originate from the CMTS side.If the modem itself were faulty:- it would reboot randomly without any preceding signal errors- kernel panics would occur without timing or synchronization problems- there would be no SYNC Timing Synchronization failures- there would be no T3 timeouts- the DS profile would not change- the DOCSIS 3.1 lock would not drop or become unstable

DOCSIS issue | Virgin Media Community

14 Replies

Client62
Alessandro Volta
22 days ago
Intel Atom CPU Kernel Panic Restarts are a fault of the Intel CPU in the VM Hub.
The only fix is to request a replacement VM Hub.

If you have DOCSIS signal level concerns, share the contents of the Upstream and Downstream
status tabs for review.
- Amithyel
  Tuning in
  21 days ago
  This is the 2nd hub I got within a year. I don't think is the issue.
  - Client62
    Alessandro Volta
    21 days ago
    Look at the last entry in the log you posted.
    
    We can all see the kernel panic message.
    
    This is a defective Hub.
gitty
On our wavelength
21 days ago
Can you post a more complete log (as text)? The events just after a crash/reboot are somewhat meaningless.
- Amithyel
  Tuning in
  21 days ago
  The log shows the exact same thing for the last 2 weeks without any changes. (I removed the MAC)
  
  17-11-2025 07:57:19 notice GUI Login Status - Login Success from LAN interface
  16-11-2025 17:17:56 notice GUI Login Status - Login Success from LAN interface
  16-11-2025 16:45:56 notice GUI Login Status - Login Success from LAN interface
  16-11-2025 16:40:48 notice CM-STATUS message sent. Event Type Code: 16; Chan ID: 41; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 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;
  16-11-2025 16:40:35 notice REGISTRATION COMPLETE - Waiting for Operational status
  16-11-2025 16:40:23 notice 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;
  16-11-2025 16:40:20 warning DHCP WARNING - Non-critical field invalid in response ;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
  16-11-2025 16:40:18 notice Honoring MDD; IP provisioning mode = IPv4
  16-11-2025 16:40:11 critical 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;
  16-11-2025 16:40:05 critical 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;
  16-11-2025 16:40:02 critical Cable Modem Reboot because of - kernel-panic
  16-11-2025 08:27:09 critical 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;
  16-11-2025 08:27:03 critical 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;
  16-11-2025 08:27:02 critical Cable Modem Reboot because of - kernel-panic
  05-11-2025 19:58:05 critical 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;
  05-11-2025 19:57:58 critical Cable Modem Reboot because of - HW or Power-On Reset
  05-11-2025 19:57:58 critical 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;
  05-11-2025 19:54:17 critical 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;
  05-11-2025 19:54:11 critical 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;
  05-11-2025 19:54:10 critical Cable Modem Reboot because of - kernel-panic
  29-10-2025 11:35:02 critical 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;
  29-10-2025 11:34:55 critical 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;
  29-10-2025 11:33:57 critical 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;
  29-10-2025 11:28:14 critical 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;
  29-10-2025 11:24:08 critical 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;
  28-10-2025 19:59:42 critical 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;
  28-10-2025 19:59:37 critical Cable Modem Reboot because of - kernel-panic
  28-10-2025 19:59:37 critical 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;
  23-10-2025 16:55:07 critical Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
  23-10-2025 16:55:07 critical 16 consecutive T3 timeouts while trying to range on upstream channel 8;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1;
  23-10-2025 16:55:01 critical 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;
  23-10-2025 16:10:21 critical 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;
  23-10-2025 16:10:17 critical 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;
  23-10-2025 16:10:16 critical Cable Modem Reboot because of - Reboot UI
  23-10-2025 15:19:44 critical 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;
  - gitty
    On our wavelength
    18 days ago
    All the sync fails are logged just after the halt, so we cannot conclude anything about the signal quality from that. What triggers the halt...?
    Do you see more of those event 16 that flags profiles 1, 2 and 3?

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