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user_gjlxgd
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Thursday, August 13th, 2026 3:42 PM

Connection drop outs every 20 minutes

I have tried two modems. Netgear CM3000 and Motorola MB8611. They both exhibit the same issues. I have replaced the wall plate/coax outlet in the room. I then took the cable that runs directly to my house and ran it directly to my modem. Same issue. Techs come out and say nothing is wrong and move on. There is something very wrong. I've tried three different routers. I've tried multiple WAN ports on my router, I've tried different ethernet cables. I've factory reset my router. I've factory reset my modem. I'm about to have to cancel and go to Starlink in downtown Baltimore because of the Xfinity monopoly.

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4 hours ago

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EG

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5 hours ago

What do the modem's signal status values look like ? Try getting them here; http://192.168.100.1 


Please 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.

Is there a router / WiFi in the mix ?

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EG

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4 hours ago

The signal status values were good at that snapshot in time.

Your post of the error log entries was marked as being "Private" by the forum bot because it contains CM MAC and the CMTS MAC addresses. They are considered to be personal information. The posting of personally identifiable information is a violation of their forum guidelines. Please redact them.

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user_gjlxgd

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Sorry, I did the CM-MAC but not CMTS.

Thu Aug 13 10:39:39 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Thu Aug 13 10:22:27 2026 Notice (6) DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM_QOS=1.1;CM-VER=3.1;
Thu Aug 13 10:22:22 2026 Notice (6) TLV-11 - unrecognized OID;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Time Not Established Notice (6) Honoring MDD; IP provisioning mode = IPv6
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Thu Aug 13 10:21:09 2026 Critical (3) Resetting the cable modem due to docsDevResetNow
Thu Aug 13 09:03:02 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Thu Aug 13 09:01:40 2026 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Thu Aug 13 08:49:57 2026 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Thu Aug 13 07:47:01 2026 Critical (3) Resetting the cable modem due to docsDevResetNow
Thu Aug 13 00:37:19 2026 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Thu Aug 13 00:36:59 2026 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Wed Aug 12 02:09:25 2026 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Mon Aug 10 02:09:52 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Sun Aug 09 16:46:50 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Fri Aug 07 14:28:19 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Wed Aug 05 11:27:40 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Sun Aug 02 17:32:52 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Sun Aug 02 15:03:19 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Thu Jul 30 09:50:39 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Mon Jul 27 16:49:08 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Mon Jul 27 11:30:23 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Sun Jul 26 07:25:06 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Sat Jul 25 15:36:18 2026 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Fri Jul 24 11:38:52 2026 Critical (3) Resetting the cable modem due to docsDevResetNow
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Fri Jul 24 11:32:43 2026 Critical (3) SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) No Ranging Response received - T3 time-out;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=(mac address);CMTS-MAC=(cmts mac address);CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) Resetting the cable modem due to docsDevResetNow

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4 hours ago

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XfinityJosephA

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user_gjlxgd feel free to send us a direct message so we can access your account and take a closer look at your modem and connection. Just include your name and service address. 
 

To do so, click on the chat icon located at the top right of this forum's page. Here are 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 "Start new conversation" (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

 

 

https://forums.xfinity.com/conversations/guidelines/how-to-direct-messaging-within-the-forum/697ba1e570934d009185c514

 

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4 hours ago

EG

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4 hours ago

No worries ! So even though the signal status values looked OK at that snapshot in time, the error log entries confirm that something is going on. Perhaps there is noise ingress into the line(s) / an upstream channel / return path impairment somewhere.


There are other signal stat values 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 (The Digital Care Team) who are available to these boards. They will be able to poll the CMTS (Cable Modem Termination System) to check for any real-time degradation and / or error reports, see your node / cable plant, and modem health, and see whether or not everything is in the green zone. They can also see a history plot for the modem and check those upstream receive signal stats.

You should get a reply here in your topic. Good luck !

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