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)
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).
Solved! Go to Solution.
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.
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?
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 !
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.
@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!