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Frequent internet drops daily

SevenLions
Frequent Visitor

Frequent internet drops daily

Equipment:

  • Arris SB6141 Cable Modem
  • Linksys AC1900 Router
  • Modem is connected directly to exterior box - no splitters - just a single coupler between the Comcast-provided coax cable and the Comcast-terminated service line

 

We have been having multiple failures to reach the internet each day. Each instance lasts about 10-15 seconds, and they can occur several times an hour. This is a real issue for the modern world.

 

The issue appears to be with the cable modem connection. I have connected a single laptop to the modem and logged pings to 8.8.8.8 overnight. Several periods of unreachability occured each time.

 

I'm not entirely sure which screens are most useful from my cable modem console, but the following log seems relevant. In fact, I found this forum by googling the verbose errors.

 

May 27 2020 10:00:52 3-Critical R04.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=20:3d:66:06:07:d4;CMTS-MAC=5c:83:8f:06:85:5b;CM-QOS=1.1;CM-VER=3.0;
May 27 2020 10:00:12 3-Critical R05.0 Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=20:3d:66:06:07:d4;CMTS-MAC=5c:83:8f:06:85:5b;CM-QOS=1.1;CM-VER=3.0;
May 27 2020 09:59:52 3-Critical R04.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=20:3d:66:06:07:d4;CMTS-MAC=5c:83:8f:06:85:5b;CM-QOS=1.1;CM-VER=3.0;
May 27 2020 09:59:52 3-Critical R05.0 Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=20:3d:66:06:07:d4;CMTS-MAC=5c:83:8f:06:85:5b;CM-QOS=1.1;CM-VER=3.0;
May 27 2020 09:59:32 3-Critical R04.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=20:3d:66:06:07:d4;CMTS-MAC=5c:83:8f:06:85:5b;CM-QOS=1.1;CM-VER=3.0;
May 27 2020 09:58:52 3-Critical R05.0 Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=20:3d:66:06:07:d4;CMTS-MAC=5c:83:8f:06:85:5b;CM-QOS=1.1;CM-VER=3.0;
May 27 2020 09:58:33 3-Critical R04.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=20:3d:66:06:07:d4;CMTS-MAC=5c:83:8f:06:85:5b;CM-QOS=1.1;CM-VER=3.0;
May 27 2020 09:58:32 3-Critical R05.0 Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=20:3d:66:06:07:d4;CMTS-MAC=5c:83:8f:06:85:5b;CM-QOS=1.1;CM-VER=3.0;
May 27 2020 09:58:13 3-Critical R04.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=20:3d:66:06:07:d4;CMTS-MAC=5c:83:8f:06:85:5b;CM-QOS=1.1;CM-VER=3.0;
May 27 2020 09:57:33 3-Critical R05.0 Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=20:3d:66:06:07:d4;CMTS-MAC=5c:83:8f:06:85:5b;CM-QOS=1.1;CM-VER=3.0;
May 27 2020 09:57:13 3-Critical R04.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=20:3d:66:06:07:d4;CMTS-MAC=5c:83:8f:06:85:5b;CM-QOS=1.1;CM-VER=3.0;
May 27 2020 09:57:13 3-Critical R05.0 Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=20:3d:66:06:07:d4;CMTS-MAC=5c:83:8f:06:85:5b;CM-QOS=1.1;CM-VER=3.0;
May 27 2020 09:56:53 3-Critical R04.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=20:3d:66:06:07:d4;CMTS-MAC=5c:83:8f:06:85:5b;CM-QOS=1.1;CM-VER=3.0;
May 27 2020 09:56:13 3-Critical R05.0 Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=20:3d:66:06:07:d4;CMTS-MAC=5c:83:8f:06:85:5b;CM-QOS=1.1;CM-VER=3.0;
May 27 2020 09:55:53 3-Critical R04.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=20:3d:66:06:07:d4;CMTS-MAC=5c:83:8f:06:85:5b;CM-QOS=1.1;CM-VER=3.0;
May 27 2020 09:55:53 3-Critical R05.0 Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=20:3d:66:06:07:d4;CMTS-MAC=5c:83:8f:06:85:5b;CM-QOS=1.1;CM-VER=3.0;
May 27 2020 09:55:33 3-Critical R04.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=20:3d:66:06:07:d4;CMTS-MAC=5c:83:8f:06:85:5b;CM-QOS=1.1;CM-VER=3.0;
May 27 2020 09:54:53 3-Critical R06.0 Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=20:3d:66:06:07:d4;CMTS-MAC=5c:83:8f:06:85:5b;CM-QOS=1.1;CM-VER=3.0;
May 27 2020 09:54:53 3-Critical R03.0 Ranging Request Retries exhausted;CM-MAC=20:3d:66:06:07:d4;CMTS-MAC=5c:83:8f:06:85:5b;CM-QOS=1.1;CM-VER=3.0;
May 27 2020 09:54:33 3-Critical R04.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=20:3d:66:06:07:d4;CMTS-MAC=5c:83:8f:06:85:5b;CM-QOS=1.1;CM-VER=3.0;
SevenLions
Frequent Visitor

Re: Frequent internet drops daily

Please let me know what additional logs or configuration parameters would be useful, and if there are other steps I should take.

EG
Expert

Re: Frequent internet drops daily

Please also post the *Downstream Power Level*, the *Upstream Power Level*, and the *SNR* (Signal to Noise Ratio) numbers.






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I am a Customer Expert volunteering my time to help other customers here in the Forums.
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SevenLions
Frequent Visitor

Re: Frequent internet drops daily

Thanks, EB. Here is a screenshot of those numbers. I may be moderated, so I will also follow up with a paste-in of the table.

Modem stats.PNG

SevenLions
Frequent Visitor

Re: Frequent internet drops daily

As suspected, my images got moderated. So here it is in text form.

 

 

Downstream Bonding Channel Value
Channel ID 29  30  31  32  33  34  35  36 
Frequency 633000000 Hz  639000000 Hz  645000000 Hz  651000000 Hz  657000000 Hz  663000000 Hz  669000000 Hz  675000000 Hz 
Signal to Noise Ratio 37 dB  38 dB  38 dB  38 dB  38 dB  39 dB  39 dB  39 dB 
Downstream Modulation QAM256  QAM256  QAM256  QAM256  QAM256  QAM256  QAM256  QAM256 
Power Level
The Downstream Power Level reading is a snapshot taken at the time this page was requested. Please Reload/Refresh this Page for a new reading
4 dBmV   5 dBmV   5 dBmV   5 dBmV   5 dBmV   6 dBmV   5 dBmV   5 dBmV  

 

Upstream Bonding Channel Value
Channel ID
Frequency 29200000 Hz  16200000 Hz  22700000 Hz  35700000 Hz 
Ranging Service ID 396  396  396  396 
Symbol Rate 5.120 Msym/sec  5.120 Msym/sec  5.120 Msym/sec  5.120 Msym/sec 
Power Level 41 dBmV  35 dBmV  35 dBmV  37 dBmV 
Upstream Modulation [2] QPSK
[1] 32QAM
[3] 64QAM
 
[2] QPSK
[1] 16QAM
[3] 64QAM
 
[2] QPSK
[1] 16QAM
[3] 64QAM
 
[2] QPSK
[1] 32QAM
[3] 64QAM
 
Ranging Status Success  T4 TimeOut  T4 TimeOut  Success 
EG
Expert

Re: Frequent internet drops daily

The signal stats are o/k but the error log entries indicate that something is going on. Perhaps there is noise ingress into the line(s) 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 to see whether or not everything is in the green zone, see your node / cable plant and modem health, and also see a history plot for the modem. You should get a reply here in your topic. Good luck !



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I am a Customer Expert volunteering my time to help other customers here in the Forums.
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SevenLions
Frequent Visitor

Re: Frequent internet drops daily

Thanks, @EG . Here's hoping!

EG
Expert

Re: Frequent internet drops daily

Quite welcome !



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I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.
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ComcastJoeTru
Official Employee

Re: Frequent internet drops daily

Hi SevenLions. We welcome you to the Xfinity Forums and thank you for creating your first post. I can assist with further troubleshooting your intermittent connectivity issues. In order to have a better insight, I will have to poll the CMTS for real-time and historical RF signal reports from your modem, and check your local Node/Plant for signal degradation / errors. Please send me a private message and include your full name so I can access your equipment. To send a private message: click my name (ComcastJoeTru) to view my profile. Then click the link that says "Send a message" and there you can private message me. 



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Official Employees are from multiple teams within Comcast: CARE, Product, Leadership. We ask that you post publicly so people with similar questions may benefit from the conversation.
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ty-baloo
New Poster

Re: Frequent internet drops daily

I'm also having this exact issue. Been through 2 of the Xfinity Gateways and used with a separate router and without. Talked to tech support around  5 times since i started my service (less than 2 months since i started it)

SevenLions
Frequent Visitor

Re: Frequent internet drops daily

PM sent, thanks.