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Losing modem connection daily

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Losing modem connection daily

I started Xfinity service 3 months ago after moving into a new apartment.  Since then, I have had internet disruptions about once per day, lasting for 3-4 minutes each time.  This week it's gotten worse, now it's happening 5-10 times per day.  Each time, I am unable to ping the modem at 192.168.100.1.  After 3-4 minutes it comes back.  This never happens in the morning, only after noon.

Connectivity within the LAN is solid, no issues there.  All my devices are on 1GbE, no wireless.  I've asked for a technician to come check it out soon, but I'm wondering what could cause this.  I think if it were excessive noise on the coax then I should still be able to ping the modem.  Before moving here, I used this modem with Spectrum for 3 years and never had any issues, so I think the modem is okay.  Could the modem be receiving some kind of bad signal that knocks it out temporarily?  I check the modem log right after it comes back and it does not show a reboot.

The modem is Motorola SB6141.  According to this article, the upstream power level should be between 45 - 51 dBmV.  Mine is usually around 42 dBmV.  Not sure if that matters.  I have checked the modem power supply and it's steady 12.2V.  There are some uncorrectable codewords but I don't know how many is acceptable.

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Expert

Re: Losing modem connection daily


@llamafilm wrote:

Each time, I am unable to ping the modem at 192.168.100.1.  

 

That's because many models of modems also lose connectivity to their LAN interface when the WAN interface loses synchronization with / connectivity to the Comcast cable system for whatever the reason may be.

 

I think if it were excessive noise on the coax then I should still be able to ping the modem.  

 

Not necessarily. See above.

 

Could the modem be receiving some kind of bad signal that knocks it out temporarily?

 

Yes.

 

I check the modem log right after it comes back and it does not show a reboot.

 

Please post the error log entries in their entirety.

 

The modem is Motorola SB6141.  According to this article, the upstream power level should be between 45 - 51 dBmV.

 

That article is for Arris modems. You stated that you have a Motorola Modem. Regardless, it is incorrect anyway. Only the Comcast system / plant specifications matter. And at 42 dB, it is well within spec.

 

 Mine is usually around 42 dBmV.  Not sure if that matters. 

 

It's fine if it is remaining stable.

 

There are some uncorrectable codewords but I don't know how many is acceptable.

 

Please post a screenshot of the entire signal status page. Post the *Downstream Power Level*, the *Upstream Power Level*, and the *SNR* (Signal to Noise Ratio) numbers. Post the correctable and uncorrectable errors, and the error log entries as stated earlier.


 



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Re: Losing modem connection daily

Thank you for your reply.  I forgot to subscribe to this topic so I didn't see it until now.  

Here are screenshots of the logs and signal page, taken a few minutes after a dropout.  https://imgur.com/a/rtLo899

 

The Comcast technician unplugged my modem to measure the signal strength and said it looks perfect.  But I am very skeptical of his equipment because right after he measured, I noticed a large gash in the coax cable going all the way to the core (through the sheild and dielectric).  Fortunately the cable was long enough, so he just cut it out and added a new F connector.  After this, of course the signal strength is still perfect, according to his meter.

I still get dropouts for a few minutes every couple of days.

 

It's weird that the logs are not in chronological order.  I assume the 1/1/1970 entries are from right after a reboot before it has time to sync the clock?

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Re: Losing modem connection daily


@llamafilm wrote:

 I assume the 1/1/1970 entries are from right after a reboot before it has time to sync the clock?


Yes, exactly.

 

The signal stats are good but the error log entries indicate that something is going on. Perhaps there is noise ingress into the line(s) 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 !



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We ask that you post publicly so people with similar questions may benefit from the conversation.
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Re: Losing modem connection daily

Greetings, @llamafilm! I appreciate you taking the time to reach out to us here on the forums. I hope you are having an amazing day! We apologize to hear of the issues you are running into with your internet connections. We certainly understand how important it is to have a reliable connection these days with the increased work and school from home. We would like to look further into your modem signal to see what's going on. Can you please send us a PM with your first and last name so we may further assist you?

 

To send a private message, please click my name "ComcastMichael" then select "Send a Message" on the right side.


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