I have an old NETGEAR Nighthawk Smart Wi-Fi Router, R6700v1. When connected to Ethernet to the first port of my router, using a Cat 6 cable, I am only getting around 380 Mbps. When I directly connect to the modem I am getting 820 Mbps. On the product page it says that all 4 ports of gigabit Ethernet. Why am I getting such lower speeds when using my router?

Not sure if this matters but the current firmware I am running is the most recent version of FreshTomato.