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Forum Discussion
Netgear CM1200 and Xfinity losing upload speeds randomly
I recently upgraded my service with Xfinity. I was previously on their 400down/35up plan and upgraded to the 1100down/35up plan. Everything worked great for the first week and then the second week I ...
Okay, cool I can pull those up when I get a chance. So, while I was troubleshooting the modem, I hooked up my older modem I used for years which was the cm500. Would the cm500 be able to handle those speeds as well? I am pretty sure it can too. But I was having the same issue on that modem with the stable and steady download speeds but dropped to 1mbps upload.
The xfinity technician assured me that both the modems were either bad or couldn't handle the upload speeds. And I didn't really believe that.
Will need to see cable modems connections data page and event log pages please.
The CM1200 can support up to 1Gb only.
I believe the CM500 was never rated for 1Gb. I had a CM700 series once and it wasn't fully rated at 1Gb thought ISP said sometimes it could but didn't officially support it.
If your seeing slow downs regardless of either modem, there is a ISP line issue. Cable Connections page will help in that some.
I'm only having issues with upload speeds, not download.
The CM500 is a DOCSIS 3.0 device and right on the edge for providing 1 Gbps upload throughput. Primarily because it has only 4 upstream channels.
Make sure your router is configured to enable both IPv4 and IPv6.
Your CM1200 is your best option. Make connections to only output port one and make sure it is not configured for a LAG connection.
Please post a copy and paste of the modems connection status and event log page.
https://kb.netgear.com/30007/How-do-I-obtain-the-cable-connection-information-from-a-NETGEAR-cable-modem-modem-router
https://kb.netgear.com/30008/How-do-I-view-or-clear-the-event-logs-on-my-NETGEAR-cable-modem-or-modem-router
dolphinsarecool wrote:
I'm only having issues with upload speeds, not download.
Just an FYI, the CM500 is only approved for up to 372 Mbps speeds on Xfinity anymore. So if you have even slightly fast speeds, avoid your CM500. Here's the list of approved devices and their speeds: https://assets.xfinity.com/assets/dotcom/projects/cix-4997_compatible-devices/2024.09.18%20Full%20List%20of%20Compatible%20Devices.pdf
The others are right about the CM1200; we'd need to see the cable connections and event logs to help diagnose it.
Anything else is just a crap shoot.
