a lot of similar problems could be found accross forums and internet regarding Intel(R) Ethernet Connection I218-LM or similar network cards having problem connectiong to a gigabit network. Max speed of connections is 100Mbps.
I will explain problem in details and hopefully Intel personnel will help us
Lenovo ThinkPad T440s
Intel(R) Ethernet Connection I218-LM
Drivers: latest (tried Intel and Lenovo drivers)
Cabling: Cat5e (all cables)
Switch: TPLink TL-SG1024
To eliminate all "external" problems it is not due bad cables nor switch nor any other variables.
Connecting other notebook to same RJ45 outlet with same cable normally gives 1Gbps (different network card producer). So we came to conclusion it has to be the problem with I218-LM.
-When you connect cable to RJ45 at the nootebook lan card obviously trying to negotiate 1Gbps speed what takes around 30-60sec when lan icon shows no connection. After that, connection has been estanblished but at the speed of 100Mbps.
-Forcing properties (speed&duplex) from auto negotiate to 1Gbps leads to no connection at all after cable has been connected to RJ45 at the notebook.
-Forcing properties (speed&duplex) from auto negotiate to 100Mbps leads to instant connection after cable has been connected to RJ45 at the notebook.
For some reasong 1Gbps speed can not be achieved and I kindly ask Intel personnel so investigate the problem. A lot of same issue has been around with same lan card or similar ones so I believe a lot of customers will have benefit of solving this issue.
Thanks in advanced
Thank you for contacting Intel.
Please provide us the operating system and the Lenovo* and Intel driver version numbers that you have tested.
We suggest to also report this issue to Lenovo* for possible BIOS/software updates that may resolve the issue.
We look forward to your reply.
Here are some settings that you can try:
1. Go to the adapter's Advance Properties, look for "Legacy Switch Compatibility Mode" and enable it.
2. Since you are using Windows* 10, install the hotfixes for your Windows* built. These hotfixes can improve and fix issues on Windows*.
Cumulative Update for Windows 10: March 8, 2016
Hope this help resolve the adapter speed/duplex negotiation problem. In case you still experience the same issue. We recommend to contact your system manufacturer for further support.
Thanks for writing back. I see that you will be getting in touch with Lenovo*. Hope you are able to resolve the issue at the soonest.