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Unstable download speeds using CM1000 modem with Xfinity

ihlejohn
Aspirant

Unstable download speeds using CM1000 modem with Xfinity

This morning my internet was working fine. Normally i have my cm1000 modem connected to my nighthawk x4s router and that router connects to my computer using an ethernet cable. I unplugged my computer, router and modem so i could paint my room, after plugging everything back in my internet was very unstable on my computer using ethernet and phone using wifi.
After trying to trouble shoot with xfinity and by myself I ended up connecting my modem directly to my computer using an ethernet cable but it is still acting same. The speeds are mostly in the single digits but vary from 1 Mbps to 60 Mbps and i saw one spike of 110 Mbps. I checked the channels for Correctable/uncorrectable codewords. The only channel having any issue is the downstream OFDM channel with over 13 million correctable and only 6 uncorrectable.

Anyone have any idea what I can do?

Model: CM1000|DOCSIS® 3.1
Message 1 of 9
plemans
Guru

Re: Unstable download speeds using CM1000 modem with Xfinity

Sounds like you've done half the battle isolating it to the modem. Great work! Since it was working fine before just a couple questions.

A what speeds do you pay for?

do you have a screen shot of your modem connection page?  these give us a brief overview of powerlevels etc. Keep in mind, they're only a snapshot of when you pull up the page. 

And screenshot of your modem logs? 

Have you checked your connections and cables? And not just from the wall to the modem but ALL of the connections/cables from where it (xfinity) enters the house? A sketchy cable or connection can cause interference and problems.

Did anything change when you were reinstalling? And by this I mean, remove coax splitters from line, change to a different coax.

Thanks!

Message 2 of 9
ihlejohn
Aspirant

Re: Unstable download speeds using CM1000 modem with Xfinity

Sorry it took a while I was having trouble uploading due to this issue so I had to take pictures with my phone and upload, hopefully they’re legible.
https://imgur.com/gallery/JhhxZzG

As far as I can tell the cable entering the house is the same as it was before but I can’t be sure. I’m using the same coax and it is tightened securely. Nothing has changed besides only using the modem at the moment. The problem feels worse than when I originally posted and there were obviously an increase in uncorrectable codewords.
After trying to upload those images channel 31 (channel ID 33) had 3824 uncorrectable codewords and 3609 correctable. But I’m not going to try to get another screenshot of that haha. And the ofdm channel increased to 203 uncorrectable.
Message 3 of 9
ihlejohn
Aspirant

Re: Unstable download speeds using CM1000 modem with Xfinity

Forgot to mention I pay for 150 Down and it regularly tests at 200.
Message 4 of 9
plemans
Guru

Re: Unstable download speeds using CM1000 modem with Xfinity

Does the coax enter from a wall plate? Did you open it when you painted? I'd specifically check there as well as replace the cable from the plate to the modem if you have a spare.
Message 5 of 9
plemans
Guru

Re: Unstable download speeds using CM1000 modem with Xfinity

I've also seen cables get jammed back into boxes and get kinked, which can cause issues. Something to check
Message 6 of 9
ihlejohn
Aspirant

Re: Unstable download speeds using CM1000 modem with Xfinity

So I went to sleep after replying last night and now that I've woken up everything is back to normal testing at 180 Mbps using xfinity's speed test. Last night xfinity support confirmed the signal was good and i should not have reduced speeds so I'm not sure what was wrong or why it's working properly now. Thank you for taking the time to help though!

Message 7 of 9
plemans
Guru

Re: Unstable download speeds using CM1000 modem with Xfinity

Glad to hear everything is working well now! Let us know if the problem comes back

Message 8 of 9
vkdelta
NETGEAR Expert

Re: Unstable download speeds using CM1000 modem with Xfinity

you can check for next few days. 

 

sometimes there is congestion and other node issues which are not related to your house.

 

as a side note, your power levels are unbalanced. 

 

DS power is quite hot. It needs to get dropped by at least 3-5 dB.

US power is quite high as well. It needs to be dropped by 10dB

Message 9 of 9
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