Simple Answer:
Generation 2 is not Supported for CentOS 6.x, Nethserver 6.x is based on.
https://technet.microsoft.com/library/dn770158(ws.11).aspx#BKMK_OS
Generation 2 machines have a much thinner Hardwarelayer. Because of this, they removed the support of many legacy devices. You can read more details here:
https://technet.microsoft.com/en-us/library/dn282285.aspx
Or more technical:
Is Nethserver 7.x based on CentOS7? If yes, regarding the MS-Docs it should work, if UEFI is activated and SecureBoot disabled.