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Intermittent dropped connection [ [RESOLVED: SEE BOTTOM POST]

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Intermittent dropped connection [ [RESOLVED: SEE BOTTOM POST]

Starting about 10 days ago, I started experiencing intermittent dropped connections on my line. It occurs perhaps a few times an hour for just a couple seconds each, but then every 1-3 hours the connection might go down for as long as 1-2 minutes, and sometimes even a little longer. I finally called Comcast today, and let the technician talk me into replacing my modem (my old modem was "at end of life" and a likely culprit, she said.)  Unfortunately, the new modem did not stop the drop outs.  (The technician also talked me into uograding to Gigabit service, but that's another topic...)

 

Modem: Netgear Nighthawk CM1000.

Router: TP Link Archer 1200

 

(Note: The problem persists even when I connect my pc directly to the modem via ethernet.)

 

Here are my downstream levels, upstream levels, and error log.

(In case the pics below don't show up, duplicates are posted at https://imgur.com/a/BppDqox)

 

Screenshot_2019-08-09 NETGEAR Modem CM1100.pngScreenshot_2019-08-09 NETGEAR Modem CM1100(1).pngScreenshot_2019-08-09 NETGEAR Modem CM1100(2).png

 

I see a lot of "range on upstream" errors, but I have little idea what that means. During the dropouts the Upload light on my modem seems to be off (while the other lights are normal/green).

 

Thank you!

Frequent Visitor

Re: Intermittent dropped connection

A couple of things I forgot to mention:

 

1. The dropouts seem to have started right after after a widespread outage in my city about 10 days ago. I don't know if they might be related to the outage or to what Comcast did to fix the outage.

 

2. I first noticed a couple days ago that I have no ipv6 connectivity. When I click on my Ethernet Status, it shows "No network access" for ipv6. I've tried every suggestion I found online but still can't get an ipv6 address. Comcast says they don't see anything wrong with the ipv6 signal they send to my modem. This may or may not be related to my dropped connections issue.

 

By the way, in the 15 minutes between my posts the modem has accumulated about 20 more errors.

Expert

Re: Intermittent dropped connection

The upstream power is too high / out of spec on channel 3 , and it may be intermittently fluctuating even higher to out of spec levels on the rest of the channel. Seems that here is some sort of an upstream / return path impairment present. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, and latency problems.

In a self troubleshooting effort to try to obtain better connectivity / more wiggle room, check to see if there are there any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1002 MHz, bi-directional, and no gold colored garbage types like GE, RadioShack, RCA, Philips, Leviton, Magnavox, and Rocketfish from big box stores like Home Depot, Lowes, Target, Wal-Mart etc. Splitters should be swapped with known to be good / new ones to test

If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two way splitter connected directly off of the drop from the street/pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed, and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.


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Frequent Visitor

Re: Intermittent dropped connection

Thanks. I've checked my wiring and don't see anything loose. I only have one splitter inside my apt and it looks fine as well.

A couple additional data points:

1. My next door neighbor in the same building said she started having the same problem at around the same time.

My downstairs neighbor says he has the same issue too, but it started a couple weeks earlier for him.

2. It now takes 15-20 minutes to get back on line whenever I restart my modern, whereas it used to take 2-3. I checked the log for the period while the modem is attempting to reestablish a connection, and the new error messages (in addition to the T3 upstream timeouts) are: 

 

"RNG-RSP CCAP Commanded Power in Excess of 6 dB Below the Value Corresponding to the Top of the DRW"

"Dynamic Range Window violation"

Does this all point to an issue with external wiring?

Expert

Re: Intermittent dropped connection

It could be external from the premises, or it could be the internal building wiring / hardware. If you are in a multiple dwelling type of building, they are known to be especially problematic !



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Re: Intermittent dropped connection

Update: A technician came out today and resolved the issue. 

 

The problem was that one of my neighbors had severe ingress (noise) on her line. (Ironically, she was the only one in my bulding that said she hadn't noticed a deterioration in service.) A second neighbor had minor ingres. A Comcast tech "fixed" the problem by putting a filter on our entire building 2 weeks ago, which effectively spread the problem to all of us. 

 

A couple thoughts that might help others in a similar situation:

 

1. Don't believe the Level 1 phone agent if they tell you the line looks fine. The tech that came out today said he could see from the signal report that there was a problem on my line before he even inspected my wiring. The L1 agents have access to these same reports, but most of them have no idea what to look for. 

 

2. If you want complete resolution of a problem you may need to be persistent. A prior tech had put in a filter for our entire building rather than isolating and fixing the source of the problem. Their thinking was probably that most affected customers would just accept it and move on.

Expert

Re: Intermittent dropped connection

Good to hear this ! Curious to see what the stats look like now ?


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Re: Intermittent dropped connection

@EG As you correctly pointed out, the upstream power level was a red flag. They are now down to 40.3 - 41.0 dBmV. The modem has logged no errors since the restart either. Finally the modem takes only 2 minutes to reboot now, where it was taking up to 20 minutes before.

 

Thanks for your help!

Expert

Re: Intermittent dropped connection [ [RESOLVED: SEE BOTTOM POST]

Quite welcome ! Happy surfing !


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