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user_d6db27
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Tuesday, January 11th, 2022 6:18 PM

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Internet dropping/recycling - Timing Synchronization failure - Motorola MB8611

I recently came home from vacation on Sat, January 8th, and my internet kept dropping. I have a new Motorola MB8611 cable model that's been working since November 2021, connected to a Netgear wireless router. Computer connections are hard line ethernet. I've troubleshot for the last few days, and finally narrowed it down to my cable model constantly dropping connection, losing its Xfinity IP. The MB8611 cable modem error logs show reoccurring "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing" and "No Ranging Response received - T3 time-out" errors. The dropping seems to be much worse in the morning, and also seems to occur when I spike my bandwidth like trying to watch a video. The drops are random and unpredictable, and I can't seem to force it to happen.

I've called Xfinity support, but they tried to blame it on me, and said since my connection was up at the time of the call, there wasn't an issue. However, they did agree to have a technician come out on Jan 13th. I live in Colorado Springs, CO.

I'm seeing many, many other posts about this same type of issue happening over the last few weeks, and mostly with Motorola modems. Every Xfinity support response seems to be "cut and paste". Does Xfinity not see a potential pattern here and system wide problem?

Please help!

Event Log  
  
    Time    Priority    Description 
    Time Not Established   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-QOS=1.1;CM-VER=3.1;
    Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;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-QOS=1.1;CM-VER=3.1;
    09:53:42
Tue Jan 11 2022		   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;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-QOS=1.1;CM-VER=3.1;
    Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;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-QOS=1.1;CM-VER=3.1;
    Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;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-QOS=1.1;CM-VER=3.1;
    Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;CM-QOS=1.1;CM-VER=3.1;
    Time Not Established   Notice (6)   Honoring MDD; IP provisioning mode = IPv6
    10:16:03
Tue Jan 11 2022		   Notice (6)   DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-QOS=1.1;CM-VER=3.1;
    10:16:25
Tue Jan 11 2022		   Notice (6)   CM-STATUS message sent. Event Type Code: 24; Chan ID: 48; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0.;CM-QOS=1.1;CM-VER=3.1;

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3 years ago

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EG

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107.7K Messages

3 years ago

What do the modem's signal stats 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.

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user_d6db27

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9 Messages

3 years ago

Connection
   Startup Sequence    
   Startup Step Status Comment

  
   Acquire Downstream Channel 555000000 Hz Locked
  
   Upstream Connection OK Operational
  
   Boot State OK Operational

  
   Configuration File OK
  
   Security Enabled BPI+
  


   Connection Status    
   System Up Time 0 days 00h:02m:53s  
  
   Network Access Allowed  
  


   Downstream Bonded Channels  
  
   Channel Lock Status Modulation Channel ID Freq. (MHz) Pwr (dBmV) SNR (dB) Corrected Uncorrected
   1 Locked QAM256 20 555.0 5.5 38.2 0 0
   2 Locked QAM256 4 453.0 8.5 38.9 0 0
   3 Locked QAM256 5 459.0 8.4 38.9 0 0
   4 Locked QAM256 6 465.0 8.2 38.9 0 0
   5 Locked QAM256 7 471.0 8.1 38.8 0 0
   6 Locked QAM256 8 477.0 8.0 38.7 0 0
   7 Locked QAM256 9 483.0 7.8 38.8 0 0
   8 Locked QAM256 10 489.0 7.8 38.7 0 0
   9 Locked QAM256 11 495.0 7.6 38.6 0 0
   10 Locked QAM256 12 507.0 7.2 38.7 0 0
   11 Locked QAM256 13 513.0 7.1 38.6 0 0
   12 Locked QAM256 14 519.0 6.9 38.6 0 0
   13 Locked QAM256 15 525.0 6.7 38.4 0 0
   14 Locked QAM256 16 531.0 6.4 38.4 0 0
   15 Locked QAM256 17 537.0 6.1 38.4 0 0
   16 Locked QAM256 18 543.0 6.0 38.3 0 0
   17 Locked QAM256 19 549.0 5.7 38.3 0 0
   18 Locked QAM256 21 561.0 5.3 38.1 0 0
   19 Locked QAM256 22 567.0 4.9 38.0 0 0
   20 Locked QAM256 23 573.0 4.6 38.1 0 0
   21 Locked QAM256 24 579.0 4.4 37.7 0 0
   22 Locked QAM256 25 585.0 4.0 37.7 0 0
   23 Locked QAM256 26 591.0 3.7 37.6 0 0
   24 Locked QAM256 27 597.0 3.4 37.5 0 0
   25 Locked QAM256 28 603.0 3.4 37.6 0 0
   26 Locked QAM256 29 609.0 3.0 37.4 0 0
   27 Locked QAM256 30 615.0 3.0 37.4 0 0
   28 Locked QAM256 31 621.0 2.8 37.3 0 0
   29 Locked QAM256 32 627.0 2.1 37.0 0 0
   30 Locked QAM256 33 633.0 1.6 37.0 0 0
   31 Locked QAM256 34 639.0 1.6 37.0 0 0
   32 Locked OFDM PLC 48 805.0 0.6 35.8 871461 0


   Upstream Bonded Channels  
  
   Channel Lock Status Channel Type Channel ID Symb. Rate (Ksym/sec) Freq. (MHz) Pwr (dBmV)
   1 Locked SC-QAM 69 5120 16.4 35.5
   2 Locked SC-QAM 70 5120 22.8 36.3
   3 Locked SC-QAM 71 5120 29.2 37.0
   4 Locked SC-QAM 72 5120 35.6 36.8

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user_d6db27

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9 Messages

3 years ago

I received a text message from Xfinity today stating, "We fixed the issue impacting Xfinity Internet in your area." At the time, it seemed to be stable, but again, the issue happens much more in the morning and not the afternoon. However, my issue remains.

Now, I've been able to force it to happen a few times if I run a speed test (speedtest.net). When it starts to test the upload speed, about 5 to 10 seconds into it, it kills the connection. My modem's xfinity IP drops, I lose all connectivity, modem's 192.168.100.1 IP becomes unreachable, after about a minute the modem issues me a 192.168.100.10 IP for about 2 minutes, and then finally re-picks up the Xfinity 75.50.*.* IP. Error logs in the modem show the same errors as mentioned above.

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EG

Expert

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107.7K Messages

3 years ago

The signal stats are ok / in spec but the error log entries indicate 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 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 !

(edited)

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user_d6db27

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9 Messages

3 years ago

Ok, thank you. Standing by. Wondering if Xfinity is seeing this issue with other Motorola modems and the MB8611. Maybe its an Xfinity configuration issue for this modem, or a Motorola firmware issue?

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EG

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@user_d6db27

An employee contacted you in this thread 10 hours ago in this thread. Did you send that private message to Xfinity support as he requested ?

I am not a Comcast Employee.
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.

Was your question answered? Please mark an Accepted Answer!tick

3 years ago

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user_c136af

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I’m having the same issue. Went to xfinity store to swap out xfinity router. Need a tech help asap. Any ideas?

3 years ago

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EG

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@user_c136af

Please create a new topic of your own here on this board detailing your issue. Thanks. 

I am not a Comcast Employee.
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.

Was your question answered? Please mark an Accepted Answer!tick

3 years ago

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user_d6db27

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9 Messages

3 years ago

Upload speed tests still breaking it. Doing it once it hits about 375mbps. My connection seems to be dropping less after this "fix" xfinity did with me doing my regular stuff in the morning. But speedtest seems to push the download/upload high enough to break it still.

(edited)

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XfinityRaul

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1.6K Messages

Hello, @user_d6db27. We'll be more than happy to help resolve your internet service issues. Please send us a private message to get started.

 

To send a Private Message, please click on the chat icon in the top-right corner of the screen, next to the bell icon, and then type or select "Xfinity Support" to initiate a live session.

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

3 years ago

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user_d6db27

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@XfinityRaul Opened up a DM. Waiting for someone to respond. Internet just dropped again.

3 years ago

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user_766992

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1 Message

3 years ago

Did this ever get resolved? I'm having the same issue. MB8611 as well. A technician came out and changed the ground block, took out one of the splitters, and changed the wall plate. still having the same problem. Very frustrating.

(edited)

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user_d6db27

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9 Messages

@user_766992​ Had an xfinity tech come out. He said my line was clean. He swapped out my motorola modem with an xfinity modem and it is stable. Been stable ever since. So, I took my motorola modem back to best buy. I think in my case, it was the modem. I think my modem couldn't push the transmit power when I spiked the bandwidth, or it had stability issues on certain bands that were required for significant bandwidth.

3 years ago

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Brandon8791

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6 Messages

3 years ago

I have been having this issue for awhile since december. I dont think that it is this modem specifically honestly. I have swapped out 3 different modems of my own, two xfinity modems and routers, and nothing has fixed it yet. Even swapped my nighthawk routers. I think personally something bigger is going on but good luck. I know I have quite a few departments involved... Engineering, Main line, maintenance, pretty positive actual corporate is involved and been replying to me as well. Their supposed to be constantly monitoring the modem, but idk if thats actually happening. 

I will say that they are atleast attempting to fix the issue, but it sucks in the meantime. Even called Motorola and their Engineer who had been there 9 years said he hasn't seen an issue like mine. It is definitely weird.

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GSJ_2910ea

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1 Message

3 years ago

I've been having the same issue with Motorola MB8611 on Comcast since I bought it in January.  Motorola graciously replaced the modem in case some thing was unexpectedly wrong with the one I originally purchased. The issue remained. Comcast tech (level 2) came out last weekend and changed a splitter that he said should be different (originally installed by Comcast.) The issue has been worse this week. Level 5 tech came out today. He replaced the splitter the guy installed last week and replaced a ground wire.  I've lost internet 3 times since he left 20 min ago. Lots of hours trying to get resolved and lots of frustration.  

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user_d6db27

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9 Messages

@GSJ_2910ea​ its the modem man... i think it has a design flaw that craps out when it needs to transmit a large amount of data. Get a different modem. I went with xfinity's rented modem for the time being, and everything is fine. Arris makes good modems.

3 years ago

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eliezery

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2 Messages

@user_d6db27 and @GSJ_2910ea I seem to have caught this issue fairly early and I can still return my modem. Would you recommend purchasing an Arris? If so, what model?

3 years ago

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eliezery

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2 Messages

3 years ago

I am having the same issues as the users above...

  Time    Priority    Description 
    11:18:28
Wed Mar 30 2022		   Critical (3)   SYNC Timing Synchronization failure - Loss of Sync;
    Time Not Established   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
    03:07:06
Fri Apr 1 2022		   Critical (3)   SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=00:40:36:85:5a:cc;
    Time Not Established   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
    00:15:00
Wed Apr 13 2022		   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
    00:15:07
Wed Apr 13 2022		   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
    00:15:43
Wed Apr 13 2022		   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
    00:15:43
Wed Apr 13 2022		   Critical (3)   Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
    00:15:52
Wed Apr 13 2022		   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
    00:15:52
Wed Apr 13 2022		   Critical (3)   Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
    00:15:53
Wed Apr 13 2022		   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
    00:15:54
Wed Apr 13 2022		   Critical (3)   Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
    00:20:00
Wed Apr 13 2022		   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
    01:18:09
Wed Apr 13 2022		   Critical (3)   DHCP failed - RS sent, no RA received;CM-MAC=00:40:36:85:5a:cc;
    01:21:25
Wed Apr 13 2022		   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
    01:24:13
Wed Apr 13 2022		   Critical (3)   No Maintenance Broadcasts for Ranging opportunities received - T2 time-out;
    01:27:15
Wed Apr 13 2022		   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
    01:30:54
Wed Apr 13 2022		   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
    01:32:52
Wed Apr 13 2022		   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
    01:33:07
Wed Apr 13 2022		   Critical (3)   SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=00:40:36:85:5a:cc;
    02:26:58
Wed Apr 13 2022		   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
    02:27:04
Wed Apr 13 2022		   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
    02:27:49
Wed Apr 13 2022		   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
    02:27:49
Wed Apr 13 2022		   Critical (3)   Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
    02:27:49
Wed Apr 13 2022		   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
    02:27:49
Wed Apr 13 2022		   Critical (3)   Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
    02:30:10
Wed Apr 13 2022		   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
    02:30:29
Wed Apr 13 2022		   Critical (3)   SYNC Timing Synchronization failure - Loss of Sync;
    Time Not Established   Critical (3)   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;
    Time Not Established   Notice (6)   Honoring MDD; IP provisioning mode = IPv6
    10:08:18
Wed Apr 13 2022		   Notice (6)   DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1.
    10:08:35
Wed Apr 13 2022		   Notice (6)   CM-STATUS message sent. Event Type Code: 24; Chan ID: 193; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0.;CM-MAC=00:40:36:85:5a:cc;CMTS-MAC=00:90:f0:6e:04:00;CM-QOS=1.1;CM-VER=3.1;

(edited)

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EG

Expert

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107.7K Messages

@eliezery​ 

Please create a new topic of your own here on this board detailing your issue. Thanks. The original poster has not returned. 3-month-old dead thread is now being closed.
 

I am not a Comcast Employee.
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.

Was your question answered? Please mark an Accepted Answer!tick

3 years ago

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