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Struggling with frequent SYNC loss and customer support making me jump through hoops

carlosp_uk
Tuning in

Hi

My setup is that I use a VM Hub 3 in Modem Mode, with my own wireless router connected to it that provides our main home network.  We have had no issues for more than 2 years, and the more advanced setup suits us because our home network is quite complicated with wireless speakers, IOT devices, home assistant setup and so on.

In the last few weeks we've started to get frequent WAN drop-outs that seem to occur several times each day for up to 30 seconds at a time.  Internal wifi was fine, I checked our router logs and ultimately traced it to the VM Hub itself.

Via the Hub's network tools / logs, I have uncovered what appears to be a frequent loss of synchronisation - I'll post the full output (log, downstream, upstream, etc.) but we get this 5-6 times per day:

 

criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
Warning!RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;

From my perspective, this absolutely correlates with what's been going on.  We've had a lot of building work around here recently, plus lorries are always reversing into the grey on-street cabinets so it wouldn't surprise me if there is an issue with line noise or connectivity.

From my perspective, that should be enough to get a technician to visit and examine the street cabling, fibre box etc.

But, on the phone, customer support are now insisting that I re-enable Router mode on the hub, turn off our own router completely, and run a 48 hour 'experiment' to rule out what I presume is issues with our router, etc.  This is pretty disruptive.

It also feels a little pointless. Why am I having to jump through these hoops, have I missed something here or are the critical log entries in the Hub not sufficient evidence that we need somebody to check the on-street connection to the cabinet?  Is there no other way?

I actually work in an I.T. company but of course I also acknowledge I'm no expert in DOCSIS, fibre, etc. so I don't want to sound arrogant - hence the community post to canvas opinion on this!

13 REPLIES 13

carlosp_uk
Tuning in

Downstream bonded channels

Channel Frequency (Hz) Power (dBmV) SNR (dB) Modulation Channel ID

1138750000336256 qam1
21467500002.936256 qam2
31547500003.237256 qam3
41627500002.938256 qam4
51707500003.238256 qam5
6178750000338256 qam6
71867500003.238256 qam7
81947500002.938256 qam8
92027500002.938256 qam9
102107500002.738256 qam10
112187500002.536256 qam11
122267500002.737256 qam12
132347500002.538256 qam13
142427500002.238256 qam14
152507500002.538256 qam15
162587500001.938256 qam16
172667500001.738256 qam17
182747500001.938256 qam18
192827500001.738256 qam19
202907500001.538256 qam20
212987500002.438256 qam21
22306750000238256 qam22
23314750000238256 qam23
243227500002.538256 qam24



Downstream bonded channels

Channel Locked Status RxMER (dB) Pre RS Errors Post RS Errors

1Locked36.64286842522302
2Locked36.64173574116440
3Locked37.623641659039
4Locked38.917472678802
5Locked38.6169367110
6Locked38.62090127046
7Locked38.61201367367
8Locked38.9119867603
9Locked38.984166535
10Locked38.921256226373
11Locked36.6215921714578
12Locked37.6155066957
13Locked38.6556134727
14Locked38.934646375
15Locked38.994305443
16Locked38.645354490
17Locked38.668006579
18Locked38.925424670
19Locked38.622463471
20Locked38.920165091
21Locked38.917693692
22Locked38.921992771
23Locked38.920064084
24Locked38.616363260

carlosp_uk
Tuning in

Upstream bonded channels

Channel Frequency (Hz) Power (dBmV) Symbol Rate (ksps) Modulation Channel ID

13940000037512064 qam4
24620000037.5512064 qam3
36030000037.5512064 qam1
42360000036.8512064 qam10



Upstream bonded channels

Channel Channel Type T1 Timeouts T2 Timeouts T3 Timeouts T4 Timeouts

1ATDMA0000
2ATDMA0000
3ATDMA0000
4ATDMA0000

carlosp_uk
Tuning in

Network Log

Time Priority Description

05/03/2024 13:14:50noticeLAN login Success;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 12:40:56Warning!RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 12:26:11noticeLAN login Success;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 12:25:34Warning!RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 12:25:25Warning!LAN login FAILED : Incorrect Username / Password / ConnectionType;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 12:16:17Warning!RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 12:16:16criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 11:51:20Warning!RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 11:13:50noticeLAN login Success;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 11:13:47Warning!LAN login FAILED : Incorrect Username / Password / ConnectionType;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 10:56:32Warning!RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 10:56:25criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 10:55:48Warning!RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 10:55:17criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 10:54:42Warning!RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 10:54:41criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 08:33:37Warning!RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 08:33:36criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 07:44:56Warning!RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/03/2024 07:44:55criticalSYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;

Adduxi
Very Insightful Person
Very Insightful Person

Unfortunately VM will insist on the Hub being in Router mode for their troubleshooting.  You will need to do a 60 second pinhole reset and then check the logs and PostRS errors.  Ideally they should remain at zero.  Rising PostRS errors usually are a noise ingress problem.  SYNC errors relate to mostly Upstream problems but you don’t seem to have any T3 errors.

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@Adduxi wrote:

You will need to do a 60 second pinhole reset and then check the logs and PostRS errors.



They only had me do a 15 second reset, which kicked the hub out of Modem Mode and seems to have reset the firmware.  Logs have survived though.

Have I missed out on some additional benefit of the longer reset?

Client62
Hero

The 60 second RESET is required to trigger a complete return to the shipping condition, 
if the old logs are still present that full reset did not happen.

VM may not care how you switch to Router mode ( by reset or by the menu ).
In Modem mode VM can not remote access the state of the Hub.

carlosp_uk
Tuning in

Thanks all.

Today’s update: 

I’ve been running the hub in Router Mode as requested for 24 hours. One more day to go before a follow up with support. 

As predicted, it has made no difference, we are still getting WAN disconnection and the same SYNC errors are still accumulating in the hub’s log. Each loss of Internet connectivity coincides directly with the log messages. 

I can only hope this is enough to persuade the phone support team tomorrow to send out an engineer. This is a miserable experience - I wish they had just believed me in the first place. 

Adduxi
Very Insightful Person
Very Insightful Person

In the meantime setup a BQM ( if you haven't already?) and this will monitor your circuit.   www.thinkbroadband.com/ping

Post a link to the live shared graph for comments.  It's also evidence for any discussions with VM btw.  

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Good suggestion - I already set up my own external monitoring script. I might do this one too.