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cjc15
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Tuesday, August 26th, 2025

Internet Issues

I have had the same plan and the same modem router for about 14 months.

I had never had this problem before, but starting last week somewhere around 5 times a day the downstream light will start blinking, and the wifi will go down. This blinking will last a couple minutes, then the wifi will still be down for a minute or so after the light goes back to solid. Sometimes this will happen a few times an hour and sometimes it will be perfectly fine for 6 hours.

I have tried reconnecting the coax as well as power cycling a few times but the problem still persists. Does anyone have any ideas on what the issue could possibly be?

Any ideas / recommendations are welcome!

Below is the event log from my modem router, and the timestamps of problems line up directly with when the issues are.

2025-8-25, 13:57:20 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 13:57:20 Warning (5) MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 13:57:20 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 13:57:20 Warning (5) MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 13:52:30 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 13:52:30 Warning (5) MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 13:51:03 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 13:51:03 Warning (5) MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 12:58:52 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 12:58:52 Warning (5) MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 12:58:52 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 12:58:51 Warning (5) MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 12:42:05 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 12:42:05 Warning (5) MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 12:40:57 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 12:40:57 Warning (5) MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 12:29:19 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 12:29:19 Warning (5) MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 11:26:44 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 11:26:43 Warning (5) MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 10:20:49 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 10:20:49 Warning (5) MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 10:20:49 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 10:20:49 Warning (5) MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 10:13:11 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 10:13:11 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 10:13:11 Warning (5) MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 09:11:49 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 09:11:49 Warning (5) MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 09:11:49 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 09:11:49 Warning (5) MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 08:08:20 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;
2025-8-25, 08:08:20 Warning (5) MDD message timeout;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.0;



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1 day ago

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EG

Expert

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112.9K Messages

3 days ago

Please also copy all of the text in its entirety of the *Downstream Power Levels*, the *SNR's* (Signal to Noise Ratios), and the *Upstream Power Level* numbers and paste them into your next post.


What is the exact make and model number of the modem / gateway device ?

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cjc15

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4 Messages

@EG​ Thanks for the response

Attached below is the requested info. The make and model is a Netgear AC1900 C7000v2 modem router

 

Procedure

 Status Comment
Acquire Downstream Channel 585000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Security Enabled BPI+
IP Provisioning Mode Honor MDD honorMdd(4)

 
Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1 Locked QAM256 24 585000000 Hz 9.8 dBmV 40.2 dB 11 0
2 Locked QAM256 25 591000000 Hz 9.7 dBmV 39.9 dB 9 0
3 Locked QAM256 26 597000000 Hz 9.9 dBmV 40 dB 26 0
4 Locked QAM256 27 603000000 Hz 10 dBmV 40.2 dB 17 0
5 Locked QAM256 28 609000000 Hz 10 dBmV 39.9 dB 17 0
6 Locked QAM256 29 615000000 Hz 10.1 dBmV 40.2 dB 1 0
7 Locked QAM256 30 621000000 Hz 10.2 dBmV 40.1 dB 2 0
8 Locked QAM256 31 627000000 Hz 10.5 dBmV 40.4 dB 42 0
9 Locked QAM256 32 633000000 Hz 10.7 dBmV 40.6 dB 27 0
10 Locked QAM256 33 639000000 Hz 11 dBmV 40.3 dB 26 29
11 Locked QAM256 34 645000000 Hz 11.1 dBmV 41 dB 39 0
12 Locked QAM256 35 651000000 Hz 10.9 dBmV 40.6 dB 9 0
13 Locked QAM256 36 657000000 Hz 10.5 dBmV 40.3 dB 19 0
14 Locked QAM256 37 663000000 Hz 10.4 dBmV 40.3 dB 8 0
15 Locked QAM256 38 669000000 Hz 10.4 dBmV 40.1 dB 25 0
16 Locked QAM256 39 675000000 Hz 10.2 dBmV 39.6 dB 7 0
17 Locked QAM256 40 681000000 Hz 9.2 dBmV 39.9 dB 0 0
18 Locked QAM256 41 687000000 Hz 9.6 dBmV 40.5 dB 0 0
19 Locked QAM256 42 693000000 Hz 10 dBmV 40.9 dB 0 0
20 Locked QAM256 43 699000000 Hz 10.7 dBmV 40.8 dB 0 0
21 Locked QAM256 44 705000000 Hz 10.7 dBmV 41.3 dB 0 0
22 Locked QAM256 45 711000000 Hz 10.4 dBmV 41.4 dB 0 0
23 Locked QAM256 46 717000000 Hz 9.8 dBmV 40.8 dB 0 0
24 Locked QAM256 47 723000000 Hz 9.4 dBmV 40.3 dB 0 0

 
Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 4 5120 Ksym/sec 29200000 Hz 40.5 dBmV
2 Locked ATDMA 1 2560 Ksym/sec 10400000 Hz 38.5 dBmV
3 Locked ATDMA 2 5120 Ksym/sec 16400000 Hz 39.6 dBmV
4 Locked ATDMA 3 5120 Ksym/sec 22800000 Hz 40 dBmV
5 Locked ATDMA 5 5120 Ksym/sec 35600000 Hz 41.1 dBmV
6 Locked ATDMA 6 2560 Ksym/sec 40400000 Hz 41 dBmV
7 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
8 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV


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2 days ago

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EG

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112.9K Messages

2 days ago

You're quite welcome ! This may or may not be the root cause of the problem (YMMV) but it should be addressed regardless.


The downstream power is high.  It may be overdriving the front-end receiver circuit of the modem. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.


Is there a drop amplifier on the coax cable line leading to the modem ? If so, try removing / bypassing it and see. If not, you can try installing a -6 dB attenuator pad such as this one on the coax port on the rear of the modem to knock that power level down and see;

https://www.amazon.com/6db-Attenuator-Pad-1-each/dp/B0013L48XA 

Good luck ! Please post back with how things turn out.

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cjc15

Visitor

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4 Messages

@EG​ Thank you so much for the quick response! There is nothing between the cable that comes out of the wall and my modem. However, I live in an approximately 20 unit apartment building and I have no observability into what happens between the cable entering my unit and it coming off the street. I will purchase this attenuator today and update you when it comes / I install it. Thanks again!

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2 days ago

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XfinityKei

Official Employee

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1.8K Messages

@cjc15 Sounds like a plan. That's some good advice from @EG . We will also check back to see how the connection goes after your purchase. In the meantime we would like to look deeper into your signal levels from our side. Can you please direct message me your first and last name along with your full service address so that I can assist? Here's the detailed steps to direct message us:
• Click "Sign In" if necessary
• Click the "Direct Message” icon (upper right corner of this page)
• Click the "New message" (pencil and paper) icon
• Type "Xfinity Support" in the to line and select "Xfinity Support" from the drop-down list
• Type your message in the text area near the bottom of the window
• Press Enter to send your message.

(edited)

I am an Official Xfinity Employee.
Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Please, mark a reply as the Accepted Answer.tick

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1 day ago

cjc15

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@XfinityKei​ Sounds good, just sent the message

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1 day ago

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