07-05-2018 10:44 AM - edited 07-05-2018 10:47 AM
I have connected my ethernet cable to the Thunderbolt 3 Dock, which is connected to my new X1 Carbon 6th Gen. But Windows 10 shows it is only 100Mbs, no matter how many times I unplug and plug it back in and transfer rates confirm it is only 100.
So I went to the Windows 10 Device Manager and forced a 1.0 Gps connection and it works at 1 Gps (large file transfer rates confirm 1Gps).
ThinkPad TBT 3 Dock Ethernet Properties -> Advanced -> Speed & Duplex
Changed: Auto Negotiation -> 1.0 Gps Full Duplex
How do I get Auto Negotiation to work and detect this 1 Gbps automatically? If I force the 1 Gps setting Windows sees a 1.0 Gps network even when there is no ethernet cable plugged into the dock. At the other end is a simple 1Gps switch (Trendnet TEG s80g) which was auto-detected 1Gps by my previous lenovo laptop (x200 dock).
07-10-2018 01:09 PM
The switch is auto negotiating 10/100/1000 without any configuration options available.
All other devices connected to this switch reliably & repeatedly connect at 1Gps, and their settings in Windows Device Manager -> Network Adapter -> Advanced -> Speed & Duplex remain set to "Auto Negotiation".
It is only the X1 Carbon on the Thunderbolt 3 Dock that negotiates to 100. Maybe the dock isn't trying to negotiate 1Gps first (or for long enough, or properly?) and accepts 100, but it should reliably negotiate 1Gbs since manually setting it to force 1Gps works without problem.