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Forum Discussion
dannoz
Jun 18, 2025Aspirant
CM3000 Comcast Business Slow Upload
 Using the Comcast provided modem I get > 300 Mbps upload.  Changing to the CM3000 I get 30.     I've spent hours with Comcast tech support and had multiple technicians out.     Thoughts?     Cable Di...
dannoz
Jun 18, 2025Aspirant
It's connected directly to a UniFi cloud gateway Max. The speed test is run on the router directly connected to the modem.
When I connect with the Comcast provided modem CBR2-T I get 1.4 Gbps down and 400 Mbps up.
When I change to the cm3000 the downstream stays the same and the upstream drops to 35 Mbps. Firmware V5.01.02.
Comcast business is now saying that the CM3000 modem only supports 35 Mbps upstream.
FURRYe38
Jun 18, 2025Guru - Experienced User
Sounds like you'll need to use there modem on there business line.