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Cable modem restart every few minutes and cause internet disconnection. Help needed!

gogoyomangogoyoman Posts: 5
in Connectivity Jul 22, 2018


I suffered internet disconnection caused by cable modem reboot or malfunction. It happened every few hour or feww days. I tried contact technical service and on-site check. They all failed to find the root cause. I will post cable model log and hope there is a solution without switching modem. Thanks.



1. Sepctrum internet.

2. Motorola MB7420

3. ASUS AC 1300


Cable modem log

1. Connection 

Startup Sequenceimage  
   Startup StepStatusCommentimage

   Acquire Downstream Channel531000000 HzLockedimage
   Upstream ConnectionOKOperationalimage
   Boot StateOKOperationalimage

   Configuration FileOK[email protected]+bpY0Y97anetjk7OqwJSTO96image

   Connection Statusimage  
   System Up Time0 days 00h:06m:23s image
   Network AccessAllowed image

   Downstream Bonded Channelsimage image
   ChannelLock StatusModulationChannel IDFreq. (MHz)Pwr (dBmV)SNR (dB)CorrectedUncorrected
Total      00

   Upstream Bonded Channelsimage image
   ChannelLock StatusChannel TypeChannel IDSymb. Rate (Ksym/sec)Freq. (MHz)Pwr (dBmV)

   Downstream Frequency Settingimage  
   Downstream Frequency Select


2. Event log

Event Log
   Logimage image
 Time  Priority  Description 
 Time Not Established  Critical (3)  No Ranging Response received - T3 time-out;CM-MAC=00:40:36:4... 
 Time Not Established  Critical (3)  No Ranging Response received - T3 time-out;CM-MAC=00:40:36:4... 
 Time Not Established  Notice (6)  Overriding MDD IP initialization parameters; IP provisioning... 
 Sun Jul 22 16:17:27 2018   Error (4)  Missing BP Configuration Setting TLV Type: 17.8;CM-MAC=00:40... 
 Sun Jul 22 16:17:27 2018   Error (4)  Missing BP Configuration Setting TLV Type: 17.9;CM-MAC=00:40... 


  • gogoyomangogoyoman Posts: 5
    Jul 22, 2018

    Usually reboot cable modem and router will fix the connectivity but only last a couple of hours or days. 


    Here is the router log. 


    Jul 22 21:26:53 rc_service: ntp 837:notify_rc restart_diskmon
    Jul 22 21:26:53 disk_monitor: Finish
    Jul 22 21:26:55 disk monitor: be idle
    Jul 22 21:27:01 crond[441]: time disparity of 1565126 minutes detected

  • karlbeckmankarlbeckman Posts: 2,206 ✭✭✭✭
    Jul 22, 2018

    When you try to "reboot", you have to start the modem first and wait until all the LED indicators stop flashing, THEN apply power to the router and let it boot up.  You might also need to reset your router to factory defaults if it does not receive the proper network setup values from the modem. 


  • gogoyomangogoyoman Posts: 5
    Jul 23, 2018

    Thanks for the reply. 

    Yes, that's indeed the procedure I used to reboot everyting. Here is the detailed steps

    1. Turn off cable modem and router.

    2. Turn on cable modem until the globe icon stop flashing and turn to solid green light. 

    3. Turn on router and wait for connections to be estabilished. 


    But such procedure does not guarantee a reliable connection.


    Another thing I tried is to reset and restore the factory default setting for both the cable modem and router. But this fails to solve the probem as well. 


    The lastest thing I tried is to set traffice manger QoS (upload: 3Mb/s Download: 80 Mb/s) This seems to have a better connection but still fails after a few hour today. Also, this method seems stupid to me. 


    Any comment or suggestions? 

  • reds91185reds91185 Posts: 2,452
    Jul 24, 2018

    Have you checked all the coax connections from the point the cable comes in from the street to the modem for any loose connections or damaged coax?

  • gogoyomangogoyoman Posts: 5
    Jul 25, 2018

    I personally check the connection from wall plug to cable modem and the connection in the in the electrical room. Both seems to have tight coax cable connection. 


    And there was a spectrum technician check all the cable signal and found no issues. 


    Is there any other info I can provide to help debug? Thanks

  • RAIST5150RAIST5150 Posts: 644 ✭✭✭✭
    Jul 30, 2018
    Keep an eye on your upstream power levels. If you notice them increasing by more than a 1.0 swing throughout the day, there may be something injecting noise in the lines or an amp may be losing efficiency (not uncommon on hot days).

    Seeing as your downstream SNR is under 40, noise may be suspect. Double check there aren't any loose/unterminated lines. If this is not a dedicated line going ONLY to your modem, every coaxial wall jack in the house that is also fed from the drop needs to have a device on it... be that a TV, VCR, or termination cap. Any unterminated coax in the home is a potential micro-antenna. With T-Mobile taking over the 600MHz spectrum, this can once again become a critical issue for cable internet.

    If you see those upstream power levels flirting with or exceeding 50dbmv, than that may well be where they need need to start looking more closely. Around 51 or 52 typically triggers automatic reboots at those frequencies.
  • karlbeckmankarlbeckman Posts: 2,206 ✭✭✭✭
    Jul 30, 2018

    First, turn off those traffic manager functions in your router for now.  When your data flow  approaches the limits you set for upload and download speeds they add extra delays, which really screws up the Speedtest results. 

    Next, as @RAIST5150 said, disconnect any in-house cable that doesn't have a device or terminator attached.  If your existing splitter has any open, unused ports, those too MUST have terminations installed to keep the noise out! 

    What we can see of your signal levels look OK, but the SNR (Signal to Noise ratio} is below 40 on every channel.  We REALLY need to see the corrected and uncorrected data packet errors.  Those get reset to zero when you unplug power to the modem.  Let the modem run for at least six hours (preferably more than 12) and then copy and post  the signal page here.  That will give us some valuable information about your home connection.


  • gogoyomangogoyoman Posts: 5
    Sep 02, 2018



    1. I disable the traffice manager function in the router. 

    2. Install terminator for all the unconnected plugs. 


    Right after the reboot. 



    After two weeks and a few calls with spectrum service. My internet is more stable now to show log more than two days. And here is the log

      Startup Sequenceimage  
       Startup StepStatusCommentimage

       Acquire Downstream Channel531000000 HzLockedimage
       Upstream ConnectionOKOperationalimage
       Boot StateOKOperationalimage

       Configuration FileOK[email protected]5LmfYmDzP1tug1Haefbl4uimage

       Connection Statusimage  
       System Up Time3 days 07h:10m:07s image
       Network AccessAllowed image

       Downstream Bonded Channelsimage image
       ChannelLock StatusModulationChannel IDFreq. (MHz)Pwr (dBmV)SNR (dB)CorrectedUncorrected
    Total      00

       Upstream Bonded Channelsimage image
       ChannelLock StatusChannel TypeChannel IDSymb. Rate (Ksym/sec)Freq. (MHz)Pwr (dBmV)
  • karlbeckmankarlbeckman Posts: 2,206 ✭✭✭✭
    Sep 03, 2018

    Signal levels of both the downstream [DS] and upstream [US} channels are very good.  It looks like Spectrum has masked the packet errror counters since both the corrected and uncorrectable error counts are still  displaying all zeros after almost 72 hours.  That simply NEVER happens, there are always errors detected while the modem auto-ranging circuits adjust the signal levels between all of the video channnels. 

  • Julia_RJulia_R Posts: 4,183 Lead Mod
    Sep 03, 2018

    Morning All.


    Looking at the account, located with your registration information.


    I am seeing a lot of T4 timeouts. I would encourage you to contact our Social 

    Media Customer Care Team to schedule a technician.


    Twitter: @Ask_Spectrum

    Facebook: https://www.facebook.com/Spectrum

    Julia R.
    Spectrum-Social Media Customer Care
    Lead Moderator-Community Forums

This discussion has been closed.