Nighthawk C7000 AC1900 how to test if modem/router vs Comcast issue?

NOTE: I just cleared out the event log to see if I get correct timestamps or 1970 time stamps.

Thank you! Is this what you're asking for? If not, where do I find that?

Yep. The upstream power is on the high side and it may be intermittently fluctuating even higher to out of spec levels. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.

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.

No splitters that I've installed, only those put in by Comcast. I'll disconnect and spruce up and  reconnect all that I can and see if anything improves.

I'm not clear which numbers are indicative of this problem - can you be specific as to what I should be looking at and what the values should be, so that once I do what I can I can check it on my own? Thanks!

The upstream power ideally should be between 40 and 45 dB. It's all in the pinned troubleshooting tips post at the top of this board.. No one ever looks... You, by no means, wouldn't be the first...

FYI the response from the Netgear boards was "the t3/t4 errors indicate line issues. The B-INIT-RNG Failure and no ucds received upstream line issues. this indicates the ISP needs to check the line. "  So both the Comcast- and Netgear-knowledgeable folks are saying it's the line.

But of course Comcast technical support's response was "nope, it's the modem because only Netgear modems give those types of errors and look, you're connected just fine right now and what you really need to do is call us while you're having the issue [which only ever lasts for a minute or so] and also it will fix everything if you upgrade to a higher speed Internet so let me push you to do that several times during this conversation."  I pushed to get an appointment anyway, to which I got several variations on "I just want to warn you that when they determine that it's your own equipment, there will be a service charge."

So my question now is, when the tech comes here, what do I need to tell them and make sure that they test so that they don't also immediately say that it's the modem? I just have this fear that they will have zero incentive to actually troubleshoot since all they have to say is "not our equipment, not our problem."

Thanks!

Show them this thread, if they'll even look.... Good luck with it !!!

Good news: The tech assigned here heard me out (including the information from here), verified my cable modem model and age, and declared that he can't imagine that it would be the modem. He then evaluated everything from the street all the way to the modem, and while he didn't find any one big problem he found 9 different little problems that combined could have easily been the culprit: Several loose connections, a couple of corroded connections, a 4" cable segment, and a part that they stopped using years ago because it was the cause of various intermitten problems. He was so confident that it's not the cable modem that he said that if the problem isn't resolved he'll put in the notes that they need to check the lines from even further back in our neighborhood .

So I haven't looked back at the logs yet but I'm happy with the service that I received today. Thanks again for all of your help!

Quite welcome ! 

For curiosity, what do the signal status values look like now ?