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user_40514c
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Thursday, August 26th, 2021 8:36 PM

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0.0dB SNR on OFDM channel, problem?

I recently upgraded from 300 to 800 Mbs, and upgraded to a Docsis 3.1 modem at the same time. When I reboot my modem (MB8611) I start out with a decent connection, but then I get a steady stream of Event Type Codes 4,16,21,22,24 relating to the OFDM channel, and eventually my SNR on that channel drops from around 40 to 0.0

My modem is connected to the cable coming into the house with only a short cable, barrel connector, and a 5-1000 filter. All tightly connected and decent quality. 

The internet suffers from stutters during this whole process making video conferences at work untenable. I'm ready to go back and beg for my old slow internet back, at least it was functional.

Thanks,

Nate

Connection
   Startup Sequence    
   Startup Step Status Comment

  
   Acquire Downstream Channel 549000000 Hz Locked
  
   Upstream Connection OK Operational
  
   Boot State OK Operational

  
   Configuration File OK
  
   Security Enabled BPI+
  


   Connection Status    
   System Up Time 2 days 05h:11m:46s  
  
   Network Access Allowed  
  


   Downstream Bonded Channels  
  
   Channel Lock Status Modulation Channel ID Freq. (MHz) Pwr (dBmV) SNR (dB) Corrected Uncorrected
   1 Locked QAM256 5 549.0 4.0 40.2 0 0
   2 Locked QAM256 2 531.0 3.3 39.9 0 0
   3 Locked QAM256 3 537.0 3.6 40.0 0 0
   4 Locked QAM256 4 543.0 3.7 40.0 0 0
   5 Locked QAM256 6 555.0 4.3 40.1 0 0
   6 Locked QAM256 7 561.0 4.6 40.3 1 0
   7 Locked QAM256 8 567.0 4.5 40.2 0 0
   8 Locked QAM256 9 573.0 4.2 40.2 1 0
   9 Locked QAM256 10 579.0 3.8 39.9 0 0
   10 Locked QAM256 11 585.0 3.7 39.8 0 0
   11 Locked QAM256 12 591.0 3.7 39.8 0 0
   12 Locked QAM256 13 597.0 3.7 39.7 0 0
   13 Locked QAM256 14 603.0 3.4 39.4 2 0
   14 Locked QAM256 15 609.0 3.6 39.5 0 0
   15 Locked QAM256 16 615.0 4.5 40.1 0 0
   16 Locked QAM256 17 621.0 4.9 40.5 1 0
   17 Locked QAM256 18 627.0 5.0 40.4 0 0
   18 Locked QAM256 19 633.0 5.1 40.4 2 0
   19 Locked QAM256 20 639.0 4.9 40.2 2 0
   20 Locked QAM256 21 645.0 4.9 40.2 0 0
   21 Locked QAM256 22 651.0 4.9 40.2 1 0
   22 Locked QAM256 23 657.0 4.8 40.0 1 0
   23 Locked QAM256 24 663.0 6.5 40.2 0 0
   24 Locked QAM256 25 669.0 7.1 40.9 0 0
   25 Locked QAM256 26 675.0 6.9 40.5 0 0
   26 Locked QAM256 27 681.0 6.6 40.9 3 0
   27 Locked QAM256 28 687.0 6.2 40.5 1 0
   28 Locked QAM256 29 693.0 5.9 40.2 8 0
   29 Locked QAM256 30 699.0 5.9 40.3 10 0
   30 Locked QAM256 31 705.0 5.7 40.1 8 0
   31 Locked QAM256 32 711.0 5.3 39.9 14 0
   32 Locked OFDM PLC 37 762.0 7.5 0.0 1637215248 31205


   Upstream Bonded Channels  
  
   Channel Lock Status Channel Type Channel ID Symb. Rate (Ksym/sec) Freq. (MHz) Pwr (dBmV)
   1 Locked SC-QAM 5 5120 35.6 38.0
   2 Locked SC-QAM 6 5120 29.2 38.8
   3 Locked SC-QAM 7 5120 22.8 39.0
   4 Locked SC-QAM 8 5120 16.4 39.3
   5 Locked SC-QAM 10 2560 40.4 37.3

   Event Log  
  
    Time    Priority    Description 
    10:15:50
Thu Aug 26 2021		   Warning (5)   MDD message timeout;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:15:52
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 16; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0 1 2 3.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:16:17
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 1; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:16:21
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 4; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:18:08
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 23; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:18:09
Thu Aug 26 2021		   Warning (5)   MDD message timeout;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:18:09
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 21; Chan ID: 32; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:18:11
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 22; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:18:19
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 24; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0 1.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:18:19
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 16; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 2 3.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:18:23
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 16; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0 2 3.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:18:25
Thu Aug 26 2021		   Warning (5)   MDD message timeout;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:18:26
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 20; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:18:30
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 16; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0 1 2 3.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:18:53
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 4; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:47:02
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 22; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:47:02
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 21; Chan ID: 32; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:47:03
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 23; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:47:04
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 24; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0 1.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:47:06
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 16; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 2 3.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:47:14
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 16; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0 2 3.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:48:38
Thu Aug 26 2021		   Warning (5)   MDD message timeout;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:48:39
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 22; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:48:42
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 16; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 2 3.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:48:45
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 24; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0 1.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:48:51
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 16; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0 2 3.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:49:04
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 4; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:50:18
Thu Aug 26 2021		   Warning (5)   MDD message timeout;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:50:19
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 20; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:50:21
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 1; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:50:21
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 16; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0 1 2 3.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
    10:50:52
Thu Aug 26 2021		   Notice (6)   CM-STATUS message sent. Event Type Code: 4; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=XX:XX:XX:XX:XX:XX;CMTS-MAC=00:01:5c:a8:cc:92;CM-QOS=1.1;CM-VER=3.1;
 
 
   
 

Question

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Updated 

4 years ago

 • Edited

800

2

0

Accepted Solution

user_40514c

Visitor

 • 

2 Messages

4 years ago

TLDR: The problem was caused somewhere not on my premises, and Comcast did something to fix it. 

So everything is good now. I had a tech scheduled to come out, but in the meantime Comcast did some work in the area and all my problems cleared up. In particular my signal strengths became much more consistent, and are all within 3 dBmv instead of 4 dBmv or 5 dBmv. Downstream SNR also jumped from 40db to 43db, errors have disappeared, and my OFDM profile only fluctuates once every couple days instead of constantly. 

It'd be nice if Comcast posted the actual fix that was implemented here for the record.

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XfinityAldrik

Official Employee

 • 

2.2K Messages

4 years ago

Hello @user_40514c, thank you so much for all of this information! Could you please send our team a private message with your full name and full address? Our team can most definitely take a further look at this issue.

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 chat.

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