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06-02-2018

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X1C 6th, Thunderbolt 3 Dock, Ethernet Auto-Negotation only 100Mbs

2018-07-05, 17:44 PM

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).

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6071 Posts

10-29-2009

NC

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Re: X1C 6th, Thunderbolt 3 Dock, Ethernet Auto-Negotation only 100Mbs

2018-07-10, 13:13 PM

What is the setting on the switch?  If both the switch and the laptop are set to auto-negotiate, the result may be unpredictable.

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Re: X1C 6th, Thunderbolt 3 Dock, Ethernet Auto-Negotation only 100Mbs

2018-07-10, 20:09 PM

The switch is auto negotiating 10/100/1000 without any configuration options available.

http://www.trendnet.com/products/proddetail?prod=535_TEG-S80G

 

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.

 

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6 Posts

12-26-2018

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Re: X1C 6th, Thunderbolt 3 Dock, Ethernet Auto-Negotation only 100Mbs

2019-08-17, 5:01 AM

I am observing exactly the same behavior reported by the OP. Brand new X1C 6th and Thunderbolt 3 dock, with all updates installed including latest dock firmware. Ethernet negotiates to 100 Mbps, but advanced driver setting can force it to 1 Gbps and it works fine at that speed.

 

If I observe the status of the port on the Ethernet switch (UniFi Switch8), I observe that the X1C initially negotiates to 1 Gbps (green light) during the startup phase when the screen is displaying LENOVO in a red box. But when the Windows startup screen appears, the link drops for about 1 second and then negotiates to 100 Mbps (amber light). Perhaps this is a useful clue as to the nature of the problem.

 

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Re: X1C 6th, Thunderbolt 3 Dock, Ethernet Auto-Negotation only 100Mbs

2019-08-17, 19:30 PM

Also, if I plug the same Ethernet cable directly into the ThinkPad X1C (using the Ethernet extension dongle), the link negotiates to 1 Gbps with no problem. Therefore, the problem is in the dock or its associated drivers, not a general problem in the X1C.

 

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