Recently I took a Plan which has 400Mbps down speed and 50Mbps up, but I am getting 50 to 95 Mbps down and 10 to 15 Mbps up speed. Comcast allotted technician to resolve this issue , still I am facing the same issue. I took a new Neatgear c6900 modem which supports upto 650Mbps. Technician was saying that it has v1.01.21 firmware version and asking me to upgrade it to v1.01.26 to get that speed , In one of the questions here in this forum , I saw that " comcast has to adjust the versions automatically to based on the modem version customer has" was the comment answered by comcast administrator/official. If not comcast how do I upgrade the firmware version, otherwise why dont comcast provide the modem with that version for rent when comcast is giving 400Mbps speed plan. Please let me know what is the best way to resolve this issue.
Do a hard reset on the modem by holding down the reset button for 30 seconds and it should force a download of the newer firmware.
You should be able to see what firmware you have in the gateways admin page. Only Comcast can update the firmware true. A reset may help. Also check the speed by a wired ethernet connection and be sure you are testing on a device with a 10/100/1000 gigabit NIC, not a fast ethernet 10/100 NIC.
(By the way the upload speed for Extreme 400 is 10Mbps no DOCSIS tier on Comcast has an upload of 50Mbps yet).