Forum Discussion

welshstewie's avatar
welshstewie
Joining in
24 days ago

SYNC Timing Synchronization failure

Hello,

I seem to be suffering with occasional network disconnects from the WAN.  I'm running in modem mode with a unifi dream machine - which notifies me every time the internet connection drops.  Support want me to change the hub back to router mode which seems pointless.  

The coax cable connection looks to be tightly secured.

Any help greatly appreciated.

I've logged into the Virgin Media Hub 3 and see the following:

01/01/2026 12:23:33noticeLAN login Success;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
01/01/2026 10:37:13criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
01/01/2026 07:58:25criticalNo Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
31/12/2025 23:36:56criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
31/12/2025 23:20:10criticalNo Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
31/12/2025 20:09:26criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
31/12/2025 19:36:54criticalNo Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
31/12/2025 18:02:28criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
30/12/2025 03:19:39ErrorDHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
27/12/2025 04:29:44criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
26/12/2025 18:30:48criticalNo Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
26/12/2025 15:19:39ErrorDHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
26/12/2025 02:00:20criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
26/12/2025 01:59:25criticalNo Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
25/12/2025 23:55:29criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
23/12/2025 09:08:10criticalNo Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
23/12/2025 03:19:38ErrorDHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
22/12/2025 08:10:16criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
22/12/2025 08:07:55criticalNo Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
22/12/2025 05:34:23criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;

8 Replies

  • Roger_Gooner's avatar
    Roger_Gooner
    Alessandro Volta
    24 days ago

    It's not pointless as VM can't use TR-069 for hub management when you've got the hub acting as a dumb modem.

  • Adduxi's avatar
    Adduxi
    Very Insightful Person
    24 days ago

    VM will always request the Hub to be set back to Router mode for diagnostics.  

  • Tudor's avatar
    Tudor
    Very Insightful Person
    23 days ago

    Please could we have a full set of stats. By the way, you do not have to logon to the hub to get any of these stats, just click the button in the middle of the screen.

  • welshstewie's avatar
    welshstewie
    Joining in
    22 days ago

    Thanks for the responses. 

    I'll dump the stats here and attempt to setup a BQM... which I think is:

    https://www.thinkbroadband.com/broadband/monitoring/quality/share/58cd61a2742fe025247375787a864d8cfe02c038

    Cable Modem Status
    ItemStatusComments
    Acquired Downstream Channel (Hz)

    139000000

    Locked

    Ranged Upstream Channel (Hz)

    36600415

    Locked

    Provisioning State

    Online

    		 
    ChannelFrequency (Hz)Power (dBmV)SNR (dB)ModulationChannel ID
    1139000000-1.537256 qam1
    2147000000-1.237256 qam2
    3155000000-137256 qam3
    4163000000-0.737256 qam4
    5171000000-0.437256 qam5
    6179000000037256 qam6
    7187000000037256 qam7
    82910000000.238256 qam20
    92990000000.738256 qam21
    103070000000.738256 qam22
    113150000000.738256 qam23
    123230000000.538256 qam24
    133310000000.238256 qam25
    143390000000.537256 qam26
    153470000000.938256 qam27
    163550000000.438256 qam28
    173630000000.238256 qam29
    183710000000.538256 qam30
    193790000000.538256 qam31
    20387000000038256 qam32
    21395000000-0.438256 qam34
    22403000000038256 qam35
    234110000000.238256 qam36
    244190000000.538256 qam37



    Downstream bonded channels

    ChannelLocked StatusRxMER (dB)Pre RS ErrorsPost RS Errors
    1Locked37.35330572981038
    2Locked37.3348503439077947
    3Locked37.3109707001437
    4Locked37.6363850
    5Locked37.6178020
    6Locked37.3110300
    7Locked37.669410
    8Locked38.62420
    9Locked38.61920
    10Locked38.61160
    11Locked38.9840
    12Locked38.61230
    13Locked38.62480
    14Locked37.61650
    15Locked38.69711
    16Locked38.9890
    17Locked38.91135
    18Locked38.91850
    19Locked38.611116
    20Locked38.62830
    21Locked38.62150
    22Locked38.613623
    23Locked38.91180
    24Locked38.91240

    Upstream bonded channels

    ChannelFrequency (Hz)Power (dBmV)Symbol Rate (ksps)ModulationChannel ID
    13660041549.5512064 qam8
    24960000048.8512064 qam6
    33010000050.3512064 qam9
    44310000049512064 qam7
    52360000551512064 qam10

     

    Upstream bonded channels

    ChannelChannel TypeT1 TimeoutsT2 TimeoutsT3 TimeoutsT4 Timeouts
    1ATDMA0060
    2ATDMA0040
    3ATDMA0090
    4ATDMA0040
    5ATDMA0090

    General Configuration

    Network access

    Allowed

    Maximum Number of CPEs

    1

    Baseline Privacy

    Enabled

    DOCSIS Mode

    Docsis30

    Config file

    cmreg-vmdg505-bbt060-b.cm



    Primary Downstream Service Flow

    SFID380908
    Max Traffic Rate287500061
    Max Traffic Burst42600
    Min Traffic Rate0



    Primary Upstream Service Flow

    SFID380907
    Max Traffic Rate27500061
    Max Traffic Burst42600
    Min Traffic Rate0
    Max Concatenated Burst42600
    Scheduling TypeBestEffort
    TimePriorityDescription
    02/01/2026 15:19:39ErrorDHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=48:d3:43:4c:d2:7b;CMTS-MAC=00:01:5c:7a:cc:52;CM-QOS=1.1;CM-VER=3.0;
    02/01/2026 04:37:27criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=48:d3:43:4c:d2:7b;CMTS-MAC=00:01:5c:7a:cc:52;CM-QOS=1.1;CM-VER=3.0;
    02/01/2026 02:08:14criticalNo Ranging Response received - T3 time-out;CM-MAC=48:d3:43:4c:d2:7b;CMTS-MAC=00:01:5c:7a:cc:52;CM-QOS=1.1;CM-VER=3.0;
    01/01/2026 21:11:57criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=48:d3:43:4c:d2:7b;CMTS-MAC=00:01:5c:7a:cc:52;CM-QOS=1.1;CM-VER=3.0;
    01/01/2026 21:10:53criticalNo Ranging Response received - T3 time-out;CM-MAC=48:d3:43:4c:d2:7b;CMTS-MAC=00:01:5c:7a:cc:52;CM-QOS=1.1;CM-VER=3.0;
    01/01/2026 15:18:24criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=48:d3:43:4c:d2:7b;CMTS-MAC=00:01:5c:7a:cc:52;CM-QOS=1.1;CM-VER=3.0;
    01/01/2026 15:17:59criticalNo Ranging Response received - T3 time-out;CM-MAC=48:d3:43:4c:d2:7b;CMTS-MAC=00:01:5c:7a:cc:52;CM-QOS=1.1;CM-VER=3.0;
    01/01/2026 13:02:4criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=48:d3:43:4c:d2:7b;CMTS-MAC=00:01:5c:7a:cc:52;CM-QOS=1.1;CM-VER=3.0;
    01/01/2026 12:23:33noticeLAN login Success;CM-MAC=48:d3:43:4c:d2:7b;CMTS-MAC=00:01:5c:7a:cc:52;CM-QOS=1.1;CM-VER=3.0;
    01/01/2026 10:37:13criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=48:d3:43:4c:d2:7b;CMTS-MAC=00:01:5c:7a:cc:52;CM-QOS=1.1;CM-VER=3.0;
    01/01/2026 07:58:25criticalNo Ranging Response received - T3 time-out;CM-MAC=48:d3:43:4c:d2:7b;CMTS-MAC=00:01:5c:7a:cc:52;CM-QOS=1.1;CM-VER=3.0;
    31/12/2025 23:36:56criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=48:d3:43:4c:d2:7b;CMTS-MAC=00:01:5c:7a:cc:52;CM-QOS=1.1;CM-VER=3.0;
    31/12/2025 23:20:10criticalNo Ranging Response received - T3 time-out;CM-MAC=48:d3:43:4c:d2:7b;CMTS-MAC=00:01:5c:7a:cc:52;CM-QOS=1.1;CM-VER=3.0;
    31/12/2025 20:09:26criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=48:d3:43:4c:d2:7b;CMTS-MAC=00:01:5c:7a:cc:52;CM-QOS=1.1;CM-VER=3.0;
    31/12/2025 19:36:54criticalNo Ranging Response received - T3 time-out;CM-MAC=48:d3:43:4c:d2:7b;CMTS-MAC=00:01:5c:7a:cc:52;CM-QOS=1.1;CM-VER=3.0;
    31/12/2025 18:02:28criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=48:d3:43:4c:d2:7b;CMTS-MAC=00:01:5c:7a:cc:52;CM-QOS=1.1;CM-VER=3.0;
    30/12/2025 03:19:39ErrorDHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=48:d3:43:4c:d2:7b;CMTS-MAC=00:01:5c:7a:cc:52;CM-QOS=1.1;CM-VER=3.0;
    27/12/2025 04:29:44criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=48:d3:43:4c:d2:7b;CMTS-MAC=00:01:5c:7a:cc:52;CM-QOS=1.1;CM-VER=3.0;
    26/12/2025 18:30:48criticalNo Ranging Response received - T3 time-out;CM-MAC=48:d3:43:4c:d2:7b;CMTS-MAC=00:01:5c:7a:cc:52;CM-QOS=1.1;CM-VER=3.0;
    26/12/2025 15:19:39ErrorDHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=48:d3:43:4c:d2:7b;CMTS-MAC=00:01:5c:7a:cc:52;CM-QOS=1.1;CM-VER=3.0;
  • welshstewie's avatar
    welshstewie
    Joining in
    22 days ago

    BQM: 

    https://www.thinkbroadband.com/broadband/monitoring/quality/share/58cd61a2742fe025247375787a864d8cfe02c038

    Hub Stats:

    ItemStatusComments
    Acquired Downstream Channel (Hz)

    139000000

    Locked

    Ranged Upstream Channel (Hz)

    36600415

    Locked

    Provisioning State

    Online

    Downstream bonded channels

    ChannelFrequency (Hz)Power (dBmV)SNR (dB)ModulationChannel ID
    1139000000-1.537256 qam1
    2147000000-1.237256 qam2
    3155000000-137256 qam3
    4163000000-0.737256 qam4
    5171000000-0.437256 qam5
    6179000000037256 qam6
    7187000000037256 qam7
    82910000000.238256 qam20
    92990000000.738256 qam21
    103070000000.738256 qam22
    113150000000.738256 qam23
    123230000000.538256 qam24
    133310000000.238256 qam25
    143390000000.537256 qam26
    153470000000.938256 qam27
    163550000000.438256 qam28
    173630000000.238256 qam29
    183710000000.538256 qam30
    193790000000.538256 qam31
    20387000000038256 qam32
    21395000000-0.438256 qam34
    22403000000038256 qam35
    234110000000.238256 qam36
    244190000000.538256 qam37



    Downstream bonded channels

    ChannelLocked StatusRxMER (dB)Pre RS ErrorsPost RS Errors
    1Locked37.35330572981038
    2Locked37.3348503439077947
    3Locked37.3109707001437
    4Locked37.6363850
    5Locked37.6178020
    6Locked37.3110300
    7Locked37.669410
    8Locked38.62420
    9Locked38.61920
    10Locked38.61160
    11Locked38.9840
    12Locked38.61230
    13Locked38.62480
    14Locked37.61650
    15Locked38.69711
    16Locked38.9890
    17Locked38.91135
    18Locked38.91850
    19Locked38.611116
    20Locked38.62830
    21Locked38.62150
    22Locked38.613623
    23Locked38.91180
    24Locked38.91240

    Upstream bonded channels

    ChannelFrequency (Hz)Power (dBmV)Symbol Rate (ksps)ModulationChannel ID
    13660041549.5512064 qam8
    24960000048.8512064 qam6
    33010000050.3512064 qam9
    44310000049512064 qam7
    52360000551512064 qam10

     

    Upstream bonded channels

    ChannelChannel TypeT1 TimeoutsT2 TimeoutsT3 TimeoutsT4 Timeouts
    1ATDMA0060
    2ATDMA0040
    3ATDMA0090
    4ATDMA0040
    5ATDMA0090

    General Configuration

    Network access

    Allowed

    Maximum Number of CPEs

    1

    Baseline Privacy

    Enabled

    DOCSIS Mode

    Docsis30

    Config file

    cmreg-vmdg505-bbt060-b.cm



    Primary Downstream Service Flow

    SFID380908
    Max Traffic Rate287500061
    Max Traffic Burst42600
    Min Traffic Rate0



    Primary Upstream Service Flow

    SFID380907
    Max Traffic Rate27500061
    Max Traffic Burst42600
    Min Traffic Rate0
    Max Concatenated Burst42600
    Scheduling TypeBestEffort

    Network Log

    TimePriorityDescription
    03/01/2026 06:59:28criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
    03/01/2026 06:32:37criticalNo Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
    02/01/2026 15:19:39ErrorDHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
    02/01/2026 04:37:27criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
    02/01/2026 02:08:14criticalNo Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
    01/01/2026 21:11:57criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
    01/01/2026 21:10:53criticalNo Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
    01/01/2026 15:18:24criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
    01/01/2026 15:17:59criticalNo Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
    01/01/2026 13:02:4criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
    01/01/2026 12:23:33noticeLAN login Success;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
    01/01/2026 10:37:13criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
    01/01/2026 07:58:25criticalNo Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
    31/12/2025 23:36:56criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
    31/12/2025 23:20:10criticalNo Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
    31/12/2025 20:09:26criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
    31/12/2025 19:36:54criticalNo Ranging Response received - T3 time-out;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
    31/12/2025 18:02:28criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
    30/12/2025 03:19:39ErrorDHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;
    27/12/2025 04:29:44criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=<<REDACTED>>;CMTS-MAC=<<REDACTED>>;CM-QOS=1.1;CM-VER=3.0;

     

  • Adduxi's avatar
    Adduxi
    Very Insightful Person
    22 days ago

    Your Upstream power is on the limit, so could be a bit lower.  Range approx. 34 to 51  There are noise issues on the Downstream, too many PostRS errors.  These should be zero or very close to.

    Your BQM is not working, you need to allow your Router to respond to pings.  At the moment, it's all red.

    Reboot the Hub and note the stats to check if the PostRS errors are rising again.

    • welshstewie's avatar
      welshstewie
      Joining in
      21 days ago

      Ok, rebooted and I've set the modem in router mode.  It's looking better:

      Also, the monitor is now working:
      https://www.thinkbroadband.com/broadband/monitoring/quality/share/58cd61a2742fe025247375787a864d8cfe02c038

      I'll continue to keep an eye on it.

      Thank you for all your help so far!

      Downstream bonded channels

      ChannelFrequency (Hz)Power (dBmV)SNR (dB)ModulationChannel ID
      1235000000-0.237256 qam13
      2243000000-0.437256 qam14
      3251000000-0.538256 qam15
      4259000000-0.437256 qam16
      5267000000-0.238256 qam17
      6275000000-0.438256 qam18
      7283000000-0.238256 qam19
      82910000000.438256 qam20
      92990000000.938256 qam21
      103070000000.938256 qam22
      113150000000.938256 qam23
      123230000000.538256 qam24
      133310000000.438256 qam25
      143390000000.737256 qam26
      15347000000138256 qam27
      163550000000.538256 qam28
      173630000000.438256 qam29
      183710000000.738256 qam30
      193790000000.738256 qam31
      20387000000038256 qam32
      21395000000-0.238256 qam34
      22403000000038256 qam35
      234110000000.438256 qam36
      244190000000.538256 qam37



      Downstream bonded channels

      ChannelLocked StatusRxMER (dB)Pre RS ErrorsPost RS Errors
      1Locked37.6240
      2Locked37.6230
      3Locked38.6480
      4Locked37.6170
      5Locked38.6170
      6Locked38.6100
      7Locked38.6160
      8Locked38.6240
      9Locked38.6210
      10Locked38.660
      11Locked38.690
      12Locked38.6130
      13Locked38.6250
      14Locked37.6170
      15Locked38.690
      16Locked38.6110
      17Locked38.6100
      18Locked38.9240
      19Locked38.9100
      20Locked38.6120
      21Locked38.690
      22Locked38.690
      23Locked38.6100
      24Locked38.6180