No matter what router I use, I only get 30 - 50% of the internet speed through it.
If I connect a laptop directly to the Comcast modem, which is in "Bridge mode" so that the connected device gets a public IP address via DHCP, I get about 100mbps. If I connect a router BETWEEN the modem and the laptop, the speed falls to 30-50. There is NO OTHER device connected to the router or the modem. I have confirmed this problem using a SonicWall TZ400, a Cisco RV180, an ASUS RT-N12, and a UTT ER518. The issue remains for each of those routers. I also used the same patch cables for each measurement. Wireless is not involved.
Why does this happen and how do I change it?