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

[jason38]

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 Step Status Comment       Acquire Downstream Channel 495000000 Hz Locked       Upstream Connection OK Operational       Boot State OK Operational       Configuration File OK d11_m_mb7621_perfselect_c01.cm       Security Enabled BPI+

Connection Status

System Up Time 2 days 16h:48m:20s         Network Access Allowed

Downstream Bonded Channels

Channel Lock Status Modulation Channel ID Freq. (MHz) Pwr (dBmV) SNR (dB) Corrected Uncorrected 1 Locked QAM256 13 495.0 15.4 38.1 1440 0 2 Locked QAM256 2 429.0 14.3 38.6 424 0 3 Locked QAM256 3 435.0 14.4 38.6 421 0 4 Locked QAM256 4 441.0 14.8 38.7 452 0 5 Locked QAM256 5 447.0 15.1 38.8 472 0 6 Locked QAM256 6 453.0 15.5 38.9 415 0 7 Locked QAM256 7 459.0 15.6 38.8 422 0 8 Locked QAM256 8 465.0 15.6 38.8 554 0 9 Locked QAM256 9 471.0 15.8 38.7 687 0 10 Locked QAM256 10 477.0 15.8 38.6 599 0 11 Locked QAM256 11 483.0 15.7 38.5 863 0 12 Locked QAM256 12 489.0 15.6 38.3 1154 0 13 Locked QAM256 1 423.0 14.4 38.8 291 0 14 Locked QAM256 14 507.0 15.5 35.6 3206 0 15 Locked QAM256 15 513.0 15.6 38.0 1946 0 16 Locked QAM256 16 519.0 15.8 37.9 1841 0 17 Locked QAM256 17 525.0 15.4 38.2 2698 0 18 Locked QAM256 18 531.0 15.5 38.0 3110 0 19 Locked QAM256 19 543.0 15.5 37.9 4080 0 20 Locked QAM256 20 549.0 15.4 38.1 3561 0 21 Locked QAM256 21 555.0 15.2 38.0 4173 0 22 Locked QAM256 22 561.0 15.0 37.8 5960 0 23 Locked QAM256 23 567.0 15.2 37.7 6168 0 24 Locked QAM256 24 573.0 15.3 37.6 6952 0 Total             51889 0

Upstream Bonded Channels

Channel Lock Status Channel Type Channel ID Symb. Rate (Ksym/sec) Freq. (MHz) Pwr (dBmV) 1 Locked ATDMA 4 5120 36.5 40.9 2 Locked ATDMA 1 5120 17.3 38.5 3 Locked ATDMA 2 5120 23.7 40.9 4 Locked ATDMA 3 5120 30.1 40.8 5 Locked ATDMA 5 1280 41.2 39.4 6 Not Locked Unknown 0 0 0 0.0 7 Not Locked Unknown 0 0 0 0.0 8 Not Locked Unknown 0 0 0 0.0

[EG]

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.

[jason38]

@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]

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...

[jason38]

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

[EG]

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.

[jason38]

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]

@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]

Yep. Right at the back.

[jason38]

@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?

[EG]

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 !

[jason38]

@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]

My pleasure !

[jason38]

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]

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".