I installed a fresh install of Debian 10 buster on my z97x system. My home connection is 300Mbps download and 15Mbps upload. I used speedtest to measure this. Selecting the same server using speedtest-cli on my Debian 10 install I get 299Mbps download and only 3.29Mbps upload.
The upload speed is super slow. I have checked the cables and switches. Direct connecting the cable to the router makes no different. I had this issue on another Debian 10 server same exact upload and download with a realtek ethernet port on the motherboard - switching to a PCIE ethernet fixes this.
Running windows on this same machine has the correct 15Mbps upload so it leads me to believe there is something going on with Debian 10 and the drivers. I can just install a PCI E nic but I would rather use the port built into this motherboard as the case has no PCI slots.
lspci output 00:19.0 Ethernet controller: Intel Corporation Ethernet Connection I217-V
EDIT #1 I have tried installing the drivers manually following these instructions: https://downloadmirror.intel.com/15817/eng/readme.txt to the best of my knowledge. The issue still persists!
Is there any other information I can gather to help fix this issue?