Sorry I forgot to give the NUC version NUC5i5RYH.
Windows Server 2012 is not supported for your Intel® NUC, this operating system has not been validated to work with this Intel® NUC and some drivers will not be available as you can see here: Intel® NUC — Supported Operating Systems
Here you can check a similar post with same respond NUC5i7RYH networking on Windows Server 2012-R2.
Thank you Amy
I will try the links you provided. I feel it is a great pity that Intel has not provided drivers for WS2012.