I saw a video where Wendell had mentioned that some 10 gig Ethernet cards needed a firmware update in order to sync correctly with 2.5 and 5 gig. Well, that was exactly the problem that I was having with the Asus xg-c100c. I update my firmware from version 3.0.8 to 3.1.88 and now the cards work just fine at 2.5 gig.
I had had one of them working in Windows 10. The firmware was not updated automatically.
There’s two different versions of Asus xg-c100c; when Asus started using the aqc113 chipset in the nic it never changed the name of it causing confusion.
I suspect this update is only applicable to the aqc107 version of this card that came in the blue retail box as opposed to the aqc113 version of the card that came in the black retail box.