This message was posted by Intel Corporation on behalf of
Hi, understand you have concern in setting your X520-DA2 from 10Gbps to 1Gbps, please help to provide information below for us to further understand your issue and setup. Thanks,
1. what is the brand and model of module installed on your X520-DA2?
2. when you mentioned "no permit", does it mean you tried to modify the speed in advanced properties of X520-DA2 in device manager but doesn't have permission to proceed? please share additional information on the error or screenshot if available.
3. if convenient, you may also run the system support utility and share to us the result. Download link of the tool - https://downloadcenter.intel.com/download/25293/Intel-System-Support-Utility
sharing the website on where you can locate tested module for X520 as reference.