I have comcast internet and my modem keeps dropping connection to internet service (C7800)

[Zevas1993]

It's been over a month now and comcast blames netgear and netgear blames comcast. I've already got a replacement modem and the issue persists so I'm blaming comcast. The connection of internet services constantly gets lost. In order to get connection back I have to reboot the router or power off the modem for 30 seconds then turn it back on. I've heard that you can backdate to a different firmware and that has fixed the issue but I can't find any info on that. Included are some screenshots of logs on the modem. Sometimes the internet lasts hours sometimes it last fifteen minutes before having to restart everything again. Is there any fix known to this?

[plemans]

I'd be blaming comcast too. You've got a lot of errors in your signal and t3 errors.

these tend to be signal issues.

Plus you've already replaced the device and are still having the issue. 

I know it works fine with comcast as I've used one and it worked fine.

also, you can't change the firmware on combo devices. its set by the isp with combo devices. 

You can try removing any splitters, amplifiers, attenuators from your line. Also, direct connect the modem to right where the coax enters the home. This prevents it from being the wiring within the home from being the issue. 

[Zevas1993]

Yea I've had them out checking the lines and everything multiple times. I know where the coax comes into the home but its an immediate splitter at that point. Everything else has been tried and tested.

[plemans]

I've had to have them install one of their modems before to prove it wasn't a 3rd party device. Stinks to have to do but they're good at blaming 3rd party equipment. 

[Zevas1993]

Used to have similar problems with the Comcast modem just not as many full drops. Which leads me to believe they are putting signals in the line that the comcast modem just doesn't recognize.

[G0atHax0r]

Hi there... I've had similiar issues, and posted similar experiences here:  https://community.netgear.com/t5/Cable-Modems-Routers/CM1000-intermittent-connection-loss-on-XFinity...

The key here is to ask Xfinity/Comcast to put a monitor on your line, so they can analyze from remote what's happening to your line.  In my case they figured out it had something to do with some equipment upstream probably at their node, which fixed it for us.  Keep an eye on your modem's Power (dBmV) and SNR/MER (dB)... they should be at 0dBmV and about 40db respectively.  If they fluctuate and drop below a certain amount, that could be causing the drops.  Like when mine went to -5dBmV and 36dB, I would start getting errors and drops.  It has now stabilized, and my internet has been stable for 4 days in a row, which I haven't seen in many months.

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@Zevas1993 wrote:
It's been over a month now and comcast blames netgear and netgear blames comcast. I've already got a replacement modem and the issue persists so I'm blaming comcast. The connection of internet services constantly gets lost. In order to get connection back I have to reboot the router or power off the modem for 30 seconds then turn it back on. I've heard that you can backdate to a different firmware and that has fixed the issue but I can't find any info on that. Included are some screenshots of logs on the modem. Sometimes the internet lasts hours sometimes it last fifteen minutes before having to restart everything again. Is there any fix known to this?

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[elindoo]

I have the same issue, have had it for months. Power levels running anywhere from +1 to -30 but mostly around the -7 to -15 range which is out of spec for this unit, should be +7 to -7. Had Comcast out 11 times, ran new cable to the house, changed splitters, amplifier, etc.They keep blaming it on the modem. I went out and bought a separate cable modem and separate router. That works fine wtih no drops so i called Netgear about it. Their tech told me it's becuase the all-in-one units are more sensitive and will drop.

Going to Comcast tomorrow once more to complain. The last tech told me power was low but there was nothing that could be done about it because I'm at the end of the street. So my question was why the heck did my unit work flawlessly for over a year and then just started dropping like crazy? I'm going to ask for a monitor to be put on my system as someone suggested. I also wonder about this: It all seemed to start happening when I changed my Comcast service from 75meg to 30. I wonder if in throttling me down its messing up the modem.

[FURRYe38]

Have the ISP check the signal and line quality UP to the modem. Be sure the ISP provisions the modem correctly.
Be sure there are no coax cable line splitters in the between the modem and ISP service box. 
Be sure your using good quality RG6 coax cable up to the modem. 
Be sure to power OFF the modem for 1 minute them back ON.
https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Mod...

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@elindoo wrote:

I have the same issue, have had it for months. Power levels running anywhere from +1 to -30 but mostly around the -7 to -15 range which is out of spec for this unit, should be +7 to -7. Had Comcast out 11 times, ran new cable to the house, changed splitters, amplifier, etc.They keep blaming it on the modem. I went out and bought a separate cable modem and separate router. That works fine wtih no drops so i called Netgear about it. Their tech told me it's becuase the all-in-one units are more sensitive and will drop.

Going to Comcast tomorrow once more to complain. The last tech told me power was low but there was nothing that could be done about it because I'm at the end of the street. So my question was why the heck did my unit work flawlessly for over a year and then just started dropping like crazy? I'm going to ask for a monitor to be put on my system as someone suggested. I also wonder about this: It all seemed to start happening when I changed my Comcast service from 75meg to 30. I wonder if in throttling me down its messing up the modem.

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