NETGEAR is aware of a growing number of phone and online scams. To learn how to stay safe click here.
Forum Discussion
Solved
CM1200 Massive Bufferbloat
CM1200 suffering massive bufferbloat issues when used with Comcast, who "supports this modem".
Current setup:
CM1200 ---> XR500 ---> Desktop computer (hard wired)
Scenario:
I recently moved out of my old place and into a new one, and my computer is now getting bufferbloat spikes of 255ms - 2000ms - causing me to have massive ping in games, voip, or even fail to upload files 1/3 of the time. The only thing I changed was my modem and location; Old modem was a CM1000. It's worth noting that my original location yielded perfect bufferbloat, and no changes have been made to the PC. PC is not the issue.
Things I've done:
- Tech Visit, placed a filter on my line to up the upstream above normal noise. Not sure if it helped or not. Doubtful.
- Called comcast an additional two times, and used their text based support. Text based support claims the modem is broken, meanwhile the 3 hour phone call support told me everything was fine and that I should contact netgear - signal str ect is great.
- Tried plugging my pc directly into the modem, issue is aggravated.
- Enabled QOS on my XR500, which mitigates some of the issue but it still spikes 250ms - 2000ms every 5 seconds.
- Replaced my modem with an identical model. Issue persists, without any variation.
- Replaced the coax cable twice, and the tech even replaced the fittings on the original cable. Currently using the comcast issued coax cable.
Modem Errors(x30 per day):
- Dynamic range window violation
- SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing
I suspect that this modem is not being configured correctly, either by comcast or netgear. I don't know enough to say for sure.
Just went out to best buy and purchased a Motorola MB8600. Issue is resolved. Will not be purchasing any netgear modems in the future and strongly advising my clients against it, the routers seem solid enough.
10 Replies
Log into the the modem and take a screen snip of your modem's cable connection page and post them back on here.
Also get your logs for us to see. Take a screen snip as its easier to interpret than a copy/paste.
You said you get worse bufferbloat when you're just running the modem. How are you testing bufferbloat?
Do you have link aggregation disabled on the cm1200?
And nothing else plugged into the cm1200?
Testing bufferbloat with dslreport, I've considered trying various software but it shouldn't matter - the issue is 100% the modem, considering comcast just checked the entire line and said it was perfect. The only thing I haven't been able to do is check with a different modem. Link aggregation is off, I've tried it on as well - no difference. There is nothing else plugged into the device other than my router - or in the case of testing just my pc with the modem, just my pc.
Then that'd be the next step.
I've got a cm1000 and cm1100 and both pass bufferbloat on xfinity.
Maybe you do have a bad one.
