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Help w/ multiple internet service interruptions. What I've tried so far...

jason38
Frequent Visitor

Help w/ multiple internet service interruptions. What I've tried so far...

Hi,

 

First, I appreciate anyone's help with this. The issue is that our family's internet keeps dropping throughout the day, every day. It comes back a few minutes later, but my kids doing remote learning and I'm working from home, so this has become a bigger issue.

 

What I've tried:

  1. I'm following this pinned guide from the support forums: https://forums.xfinity.com/t5/Your-Home-Network/Internet-Troubleshooting-Tips/td-p/3310447#
  2. I have rebooted everything multiple times.
  3. I have checked and rewired all my networking equipment to make sure the connections are not loose.
  4. I have purchased a new Motorola MB7621 and checked it's compatibility.
  5. I have inspected the line from the house to the modem. There are no splitters, only one connector for a male-to-male connection. Its been there probably for 10+ years and is covered and looks ok.
  6. I have verified my speed tier.
  7. I have tried to verify my modem's power levels are within normal ranges, which I have posted below.

 

Any suggestions at this point? Thank you again for your help.
 


   Startup Sequence
 

 

  
   Startup StepStatusComment
 

 



  
   Acquire Downstream Channel495000000 HzLocked
 

 


  
   Upstream ConnectionOKOperational
 

 


  
   Boot StateOKOperational
 

 



  
   Configuration FileOKd11_m_mb7621_perfselect_c01.cm
 

 


  
   SecurityEnabledBPI+
 

 


  


   Connection Status
 

 

  
   System Up Time2 days 16h:48m:20s 
 

 


  
   Network AccessAllowed 
 

 


  


   Downstream Bonded Channels
 

 

 
 

 


  
   ChannelLock StatusModulationChannel IDFreq. (MHz)Pwr (dBmV)SNR (dB)CorrectedUncorrected
1LockedQAM25613495.015.438.114400
2LockedQAM2562429.014.338.64240
3LockedQAM2563435.014.438.64210
4LockedQAM2564441.014.838.74520
5LockedQAM2565447.015.138.84720
6LockedQAM2566453.015.538.94150
7LockedQAM2567459.015.638.84220
8LockedQAM2568465.015.638.85540
9LockedQAM2569471.015.838.76870
10LockedQAM25610477.015.838.65990
11LockedQAM25611483.015.738.58630
12LockedQAM25612489.015.638.311540
13LockedQAM2561423.014.438.82910
14LockedQAM25614507.015.535.632060
15LockedQAM25615513.015.638.019460
16LockedQAM25616519.015.837.918410
17LockedQAM25617525.015.438.226980
18LockedQAM25618531.015.538.031100
19LockedQAM25619543.015.537.940800
20LockedQAM25620549.015.438.135610
21LockedQAM25621555.015.238.041730
22LockedQAM25622561.015.037.859600
23LockedQAM25623567.015.237.761680
24LockedQAM25624573.015.337.669520
Total      518890


   Upstream Bonded Channels
 

 

 
 

 


  
   ChannelLock StatusChannel TypeChannel IDSymb. Rate (Ksym/sec)Freq. (MHz)Pwr (dBmV)
1LockedATDMA4512036.540.9
2LockedATDMA1512017.338.5
3LockedATDMA2512023.740.9
4LockedATDMA3512030.140.8
5LockedATDMA5128041.239.4
6Not LockedUnknown0000.0
7Not LockedUnknown0000.0
8Not LockedUnknown0000.0
EG
Expert

Re: Help w/ multiple internet service interruptions. What I've tried so far...

The downstream power is too high / out of spec. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.

Is there an amplifier on the coax line leading to the modem ? If so, try bypassing it and see if the problem remains.



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jason38
Frequent Visitor

Re: Help w/ multiple internet service interruptions. What I've tried so far...

@EG - First thank you again. I can't tell you how much I appreciate your help. It's been very frustrating for my family.

 

I don't believe there is an amplifier. I had to do a good image search to know what to look for. The only connection directly from the street to the modem is this male-to-male connector (see link). This doesn't look like an amplifier.

 

https://www.dropbox.com/s/8oeg0nbeh8yrwhw/PXL_20210127_194400792.jpg?dl=0

 

Thanks

 

EG
Expert

Re: Help w/ multiple internet service interruptions. What I've tried so far...

Right. That's just the grounding block / demarcation point.

 

You can try using a 9dB loss forward path attenuator pad like the one in the link below to knock that downstream power back down in to being in spec and see. It will not affect the upstream power which is in spec / good;

 

https://www.amazon.com/FPA9-54-Forward-Attenuator-DOCSIS-Cable/dp/B08DMBWG8Q/ref=sr_1_1?dchild=1&key...



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jason38
Frequent Visitor

Re: Help w/ multiple internet service interruptions. What I've tried so far...

Awesome thanks...I've ordered the part and will give it a try.

EG
Expert

Re: Help w/ multiple internet service interruptions. What I've tried so far...

O/k just be advised that this may not be the root cause of the problem, but it should be addressed regardless. No guarantees. YMMV. Good luck with it and please post back with how things turn out.



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jason38
Frequent Visitor

Re: Help w/ multiple internet service interruptions. What I've tried so far...

Sounds good...happy to have at least something to try. I'll circle back once it arrives and I can test it for a couple days. 

jason38
Frequent Visitor

Re: Help w/ multiple internet service interruptions. What I've tried so far...

@EG - Is there a recommended placement for this device? Or can I just chain it directly to the back of the modem? Thank you!

EG
Expert

Re: Help w/ multiple internet service interruptions. What I've tried so far...

Yep. Right at the back.



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jason38
Frequent Visitor

Re: Help w/ multiple internet service interruptions. What I've tried so far...

@EG - Hi...I installed an attenuator and the downstream power levels are much lower (see attached).

 

However, our internet is still dropping. 😞

 

I've called Comcast, but they refuse to come out because they say everything looks good on their end, so it's my problem. Not sure what to do at this point.

 

Any other ideas?

Motorola-Cable-Modem-Status-Connection.png
EG
Expert

Re: Help w/ multiple internet service interruptions. What I've tried so far...

The stats are great but I'm sorry that that didn't help your problem.

 

Something else 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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jason38
Frequent Visitor

Re: Help w/ multiple internet service interruptions. What I've tried so far...

@EG - Thank again for all your help. It's much appreciated.

 

I'm going to try a few more things:

1. Factory reset on my router.

2. If that doesn't work, I'll try a different router.

3. Asking neighbors if they've been having any issues.

 

Thanks!

 

 

EG
Expert

Re: Help w/ multiple internet service interruptions. What I've tried so far...

My pleasure !



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jason38
Frequent Visitor

Re: Help w/ multiple internet service interruptions. What I've tried so far...

Just to continue documenting the issue. I have exported these recent modem logs:

 

 Log
 

 

 
 

 


  
 Time  Priority  Description 
 Time Not Established  Notice (6)  Honoring MDD; IP provisioning mode = IPv6 
 Tue Feb 02 01:19:01 2021   Critical (3)  Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=00:40:36:6d:b1:03;CMTS-MAC=00:38:df:08:b9:5f;CM-QOS=1.1;CM-VER=3.0; 
 Tue Feb 02 01:19:17 2021   Critical (3)  No Ranging Response received - T3 time-out;CM-MAC=00:40:36:6d:b1:03;CMTS-MAC=00:38:df:08:b9:5f;CM-QOS=1.0;CM-VER=3.0; 
 Tue Feb 02 01:19:28 2021   Notice (6)  Honoring MDD; IP provisioning mode = IPv6 
 Tue Feb 02 01:19:37 2021   Critical (3)  REG RSP not received;CM-MAC=00:40:36:6d:b1:03;CMTS-MAC=00:38:df:08:b9:5f;CM-QOS=1.1;CM-VER=3.0; 
 Tue Feb 02 01:31:53 2021   Critical (3)  No Ranging Response received - T3 time-out;CM-MAC=00:40:36:6d:b1:03;CMTS-MAC=00:38:df:08:b9:5f;CM-QOS=1.1;CM-VER=3.0; 
ComcastTambrey
Official Employee

Re: Help w/ multiple internet service interruptions. What I've tried so far...

Hello, @jason38! I'm really glad you took the time to reach out to us here on the Xfinity Forums for help and I appreciate you working with our wonderful expert, EG to try and troubleshoot your issue. 

I'd like to take a closer look on our end at this point to help pinpoint the cause and make sure we get you back to a stable and reliable connection. Please send me a private message with your first and last name, as well as your service address so I can assist. 

 

 To send a private message, click my name "ComcastTambrey", then click "send a message". 


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