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user_q3dmay
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3 Messages

Sunday, November 24th, 2024 10:08 PM

Modem connectivity issues

Hello,

I recently bought and installed my NETGEAR CM3000 Modem and NETGEAR RS2000 Router. My router seems to work just fine, but my modem has connectivity issues. 

My downstream power is too high at 15.3 dBmV - which goes down to 14.4 dBmV when I connect a coax cable extension but this is still outside the limits it needs to be. 

I am also getting Partial Service mode for the upstream status, but the upstream power is OK at 43.5 dBmV. 

How this is currently manifesting is in packet loss on the upload end - I get ~20% upload packet loss but little to no download packet loss. I checked the cable connections and nothing is loose or bent.. 

Anything I can do here or do I need someone to come take a look?

Thanks.

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12 days ago

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EG

Expert

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107.5K Messages

21 days ago

Yes. It may be over-driving 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.


First. 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 forward path-only 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/line-Signal-Forward-Attenuator-FPA6-54/dp/B07882H96R  You may need to use two of them piggybacked together. 

For areas that have been upgraded to the new Next Gen (mid-split) upload speeds, use this one; https://www.multicominc.com/product/multicom-mul-fpa85-forward-path-attenuator: You may need to use two of the 6dB ones piggybacked together. 

These won't affect the upload power which is within specs.

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user_q3dmay

3 Messages

@EG​ 
Thanks for responding. I can try 1 or 2 attenuators but will that affect the number of bonded upstream channels? Currently I only have 1 bonded upstream channel. 

Specs:

CM Status: Good

Downstream Status: Poor

    Downstream Power Level: Poor
    Downstream power is poor (14.5dBmV). The recommended level is between -10dBmV to 10dBmV.

    Downstream SNR Level: Good

Upstream Status: Poor

    Partial Service: Poor
    Cable modem is in partial service mode. Your service provider might be under maintenance. Most of the time it won't affect your traffic and will automatically clear when work is complete.

    Upstream Power Level: Good


Current Time: Sun Nov 24 18:48:59 2024

Startup Procedure
Acquire Downstream Channel: 669000000 Hz  Locked
Connectivity State:          OK       Operational
Boot State:                  OK       Operational
Security:                   Enabled   BPI+
IP Provisioning Mode:       Honor MDD   IPv6 only


Downstream Bonded Channels
Channel LockedStatus Modulation ChannelID  Frequency     Power    SNR   Correctables Uncorrectables     
      1     Locked     QAM256     38     669000000 Hz     14.1     41.4     6     0
      2     Locked     QAM256     10     495000000 Hz     13.8     41.4     9     0
      3     Locked     QAM256     11     507000000 Hz     13.9     41.6     4     0
      4     Locked     QAM256     12     513000000 Hz     13.8     41.5     13     0
      5     Locked     QAM256     13     519000000 Hz     13.7     41.6     11     0
      6     Locked     QAM256     14     525000000 Hz     13.8     41.5     10     0
      7     Locked     QAM256     15     531000000 Hz     14     41.6     5     0
      8     Locked     QAM256     16     537000000 Hz     14.1     41.6     724     2322
      9     Locked     QAM256     17     543000000 Hz     14.2     41.6     2     0
     10     Locked     QAM256     18     555000000 Hz     14.2     41.6     12     0
     11     Locked     QAM256     19     561000000 Hz     14.2     41.7     19     0
     12     Locked     QAM256     20     567000000 Hz     14     41.5     7     0
     13     Locked     QAM256     21     573000000 Hz     14.2     41.6     15     0
     14     Locked     QAM256     22     579000000 Hz     14     41.6     2     0
     15     Locked     QAM256     23     585000000 Hz     14     41.5     3     0
     16     Locked     QAM256     24     591000000 Hz     14.1     41.5     4     0
     17     Locked     QAM256     26     597000000 Hz     14.1     41.5     4     0
     18     Locked     QAM256     27     603000000 Hz     14.3     41.6     11     0
     19     Locked     QAM256     28     609000000 Hz     14.4     41.7     3     0
     20     Locked     QAM256     29     615000000 Hz     14.5     41.6     2     0
     21     Locked     QAM256     30     621000000 Hz     14.2     41.4     9     0
     22     Locked     QAM256     31     627000000 Hz     13.8     41.3     10     0
     23     Locked     QAM256     32     633000000 Hz     13.9     41.3     1     0
     24     Locked     QAM256     33     639000000 Hz     14     41.4     3     0
     25     Locked     QAM256     34     645000000 Hz     14.4     41.7     3     0
     26     Locked     QAM256     35     651000000 Hz     14.4     41.6     1     0
     27     Locked     QAM256     36     657000000 Hz     14.2     41.4     2     0
     28     Locked     QAM256     37     663000000 Hz     14.1     41.5     2     0
     29     Locked     QAM256     39     675000000 Hz     14.2     41.1     3     0
     30     Locked     QAM256     40     681000000 Hz     14.1     41.5     2     0
     31     Locked     QAM256     41     687000000 Hz     14.3     41.6     2     0
     32     Not Locked     Unknown      0     0 Hz     0.0     0.0     0     0

Upstream Bonded Channels (Partial Service)
Channel   LockedStatus  ChannelType ChannelID   SymbolRate        Frequency       Power     
      1       Locked       ATDMA     44       5120 Ksym/sec       35600000 Hz       43.3 dBmV
      2       Not Locked       Unknown      0       0       0       0.0
      3       Not Locked       Unknown      0       0       0       0.0
      4       Not Locked       Unknown      0       0       0       0.0
      5       Not Locked       Unknown      0       0       0       0.0
      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

Downstream OFDM Channels
Channel   LockedStatus  ProfileID  ChannelID    Frequency       Power       SNR/MER    ActiveSubcarrier    Unerror    Correctable   Uncorrectable
      1     Locked     0 ,1 ,2 ,3     25     693000000 Hz     15.28 dBmV     41.5 dB     1108 ~ 2987     428951117     416829894     231104
      2     Not Locked     0      0     0 Hz     0 dBmV     0 dB     0 ~ 4095     0     0     0

Upstream OFDMA Channels
Channel   LockedStatus    ProfileID    ChannelID    Frequency       Power
      1     Not Locked     0      0     0 Hz     0 dBmV
      2     Not Locked     0      0     0 Hz     0 dBmV

 

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21 days ago

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XfinityKrista

Official Employee

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1.5K Messages

Hello @user_q3dmay, thank you for taking the time to reach out on social media.  I understand your concern with the connection, and I'd like the opportunity to check into that for you.

 

To access your account, will you please send us a direct message with your full name and complete service address.

To do so, click on the chat icon located at the top right of this forums page.

Here's the detailed steps to direct message us:

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We ask that you post publicly so people with similar questions may benefit from the conversation.
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19 days ago

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EG

Expert

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107.5K Messages

19 days ago

@user_q3dmay 

Have you had a chance to check the line for an amp or to try the attenuators yet ? Please reply right here in your thread on these open / public help forums. There's no need to go private yet @XfinityKrista ...

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user_q3dmay

3 Messages

@EG​ Yeah, I installed the 2 attenuators and that brought down my downstream power within spec but I still only have the 1 upstream channel locked:

Cable Diagnostic

Status: Poor

Action:
[Partial Service]
If the Partial Service mode does not go away within a few hours (Click the Refresh button after each step):
1) Make sure the coaxial cable is tightly connected.
2) Remove any unnecessary splitters.
3) Replace any required ones.
4) Contact your service provider for troubleshooting help.

CM Status: Good

Downstream Status: Good

    Downstream Power Level: Good

    Downstream SNR Level: Good

Upstream Status: Poor

    Partial Service: Poor
    Cable modem is in partial service mode. Your service provider might be under maintenance. Most of the time it won't affect your traffic and will automatically clear when work is complete.

    Upstream Power Level: Good


Current Time: Mon Dec 02 19:40:25 2024

Startup Procedure
Acquire Downstream Channel: 669000000 Hz  Locked
Connectivity State:          OK       Operational
Boot State:                  OK       Operational
Security:                   Enabled   BPI+
IP Provisioning Mode:       Honor MDD   IPv6 only


Downstream Bonded Channels
Channel LockedStatus Modulation ChannelID  Frequency     Power    SNR   Correctables Uncorrectables     
      1     Locked     QAM256     38     669000000 Hz     3.9     41.7     10     25
      2     Locked     QAM256     10     495000000 Hz     2.9     41.5     0     0
      3     Locked     QAM256     11     507000000 Hz     3     41.6     0     0
      4     Locked     QAM256     12     513000000 Hz     2.8     41.6     0     0
      5     Locked     QAM256     13     519000000 Hz     3     41.6     0     0
      6     Locked     QAM256     14     525000000 Hz     2.9     41.6     0     0
      7     Locked     QAM256     15     531000000 Hz     3.2     41.7     0     0
      8     Locked     QAM256     16     537000000 Hz     3.4     41.7     0     0
      9     Locked     QAM256     17     543000000 Hz     3.5     41.7     0     0
     10     Locked     QAM256     18     555000000 Hz     3.6     41.8     0     0
     11     Locked     QAM256     19     561000000 Hz     3.6     41.7     0     0
     12     Locked     QAM256     20     567000000 Hz     3.7     41.7     0     0
     13     Locked     QAM256     21     573000000 Hz     3.6     41.8     0     0
     14     Locked     QAM256     22     579000000 Hz     3.6     41.7     0     0
     15     Locked     QAM256     23     585000000 Hz     3.6     41.7     0     0
     16     Locked     QAM256     24     591000000 Hz     3.6     41.7     0     0
     17     Locked     QAM256     26     597000000 Hz     3.7     41.7     0     0
     18     Locked     QAM256     27     603000000 Hz     4     41.8     0     0
     19     Locked     QAM256     28     609000000 Hz     4.1     41.8     0     0
     20     Locked     QAM256     29     615000000 Hz     4.1     41.8     0     0
     21     Locked     QAM256     30     621000000 Hz     3.9     41.6     0     0
     22     Locked     QAM256     31     627000000 Hz     3.6     41.5     0     0
     23     Locked     QAM256     32     633000000 Hz     3.7     41.6     20     0
     24     Locked     QAM256     33     639000000 Hz     3.8     41.6     23     0
     25     Locked     QAM256     34     645000000 Hz     4.1     41.9     21     0
     26     Locked     QAM256     35     651000000 Hz     4.2     41.8     8     27
     27     Locked     QAM256     36     657000000 Hz     4     41.7     10     24
     28     Locked     QAM256     37     663000000 Hz     4     41.7     9     24
     29     Locked     QAM256     39     675000000 Hz     4     41.3     9     27
     30     Locked     QAM256     40     681000000 Hz     3.9     41.7     5     31
     31     Locked     QAM256     41     687000000 Hz     4.1     41.8     9     26
     32     Not Locked     Unknown      0     0 Hz     0.0     0.0     0     0

Upstream Bonded Channels (Partial Service)
Channel   LockedStatus  ChannelType ChannelID   SymbolRate        Frequency       Power     
      1       Locked       ATDMA     44       5120 Ksym/sec       35600000 Hz       44.8 dBmV
      2       Not Locked       Unknown      0       0       0       0.0
      3       Not Locked       Unknown      0       0       0       0.0
      4       Not Locked       Unknown      0       0       0       0.0
      5       Not Locked       Unknown      0       0       0       0.0
      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

Downstream OFDM Channels
Channel   LockedStatus  ProfileID  ChannelID    Frequency       Power       SNR/MER    ActiveSubcarrier    Unerror    Correctable   Uncorrectable
      1     Locked     0 ,1 ,2 ,3     25     693000000 Hz     4.98 dBmV     41.7 dB     1108 ~ 2987     8111110742     7659345833     10
      2     Not Locked     0      0     0 Hz     0 dBmV     0 dB     0 ~ 4095     0     0     0

Upstream OFDMA Channels
Channel   LockedStatus    ProfileID    ChannelID    Frequency       Power
      1     Not Locked     0      0     0 Hz     0 dBmV
      2     Not Locked     0      0     0 Hz     0 dBmV

 

(edited)

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13 days ago

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EG

Expert

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107.5K Messages

12 days ago

OK so even though the signal status values look good now,  the lack of multiple bonded upstream channels is a problem. 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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