Download speed 75Mbps becomes 45 when plugged into router

[westinbrodey]

Hello,

I just got off the phone with Comcast because my download speed was about 45Mbps with ethernet cable plugged into router. I plugged the Ethernet cable directly into the modem and my speed now exceeded the 75Mbps that I am paying for. I have a Netgear N600 WNDR3400 router. I have tweaked settings on the router many different ways, but still the same results. I even researched the difference between a cat5e and cat6 Ethernet cable. Does anybody have any ideas on how I can get true download speed or close to it when the Ethernet cable is connected to the router instead of directly into the modem.

Please help.

I didn't find the right solution from the Internet.

References:-
www.cnet.com/forums/discussions/download-speed-75mbps-becomes-45-when-plugged-into-router/
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Thanks