Slow Internet Download Speed with Intel X550-T2

[groundswell]

Hi,

I recently needed to reformat my HDD and reinstall Windows 11 version 23H2. After getting everything back installed, I noticed that my internet download speeds are pretty slow on this system. Upload speeds are fine. Prior to reinstall of Windows 11, my speeds were fine.

This happened once before when I had reformatted and reinstalled Windows and the solution was to use a specific version Intel driver for this card and also the right combination of settings for the network adapter in the advanced properties for the adapter in Device Manager.

I'm hoping someone can help with the right combo!

To give further summary and troubleshooting I have tried:

• Network adapter installed is 10Gb PCI-E NIC Network Card for Intel X550-T2, 1GbE/2.5GbE/5GbE/10GbE Copper Dual RJ45 Port, with Intel ELX550AT2 controller.
• Currently have the latest Intel drivers installed for network adapter (Driver version 4.1.254.0 installed from Intel® Ethernet Adapter Complete Driver Pack version 29.2)
• Replaced all network cables on computer and router (using CAT7)
• If I do SMB file transfers to another 10GB enabled computer on my LAN, i get the full 10GB speeds (upload and download).
• I have a 5GB ATT fiber internet connection. I ran bandwidth test from router and get full speed (upload and download). 
• When running speedtest on my desktop with X550-T2, I get full upload speeds but download speeds are just over 1GB speeds.
• I tried the following settings below noted on another Intel forum post for this same model and it didn't really make any difference.

• Set Jumbo Packet to 9014 bytes

  Set Receive buffers to 4096

  Set Transmit buffers to 16384

I do believe this issue is a driver related/adapter settings related issue. I've been working in IT for 25+ years and can rule out that it's a defective adapter/faulty cables.

Hopefully someone has some recommended settings/driver version to try. I'm even open to purchasing a different model 10GB network adapter if there's one that's more compatible with Windows 11.

Thanks!