Just upgrade from 6.11.5 to 6.12, I have a Intel i350 T2 card install and also has an onboard rlt 8125 card, all working fine in 6.11.5, in system devices, it show all 3 nic, but in network settings, only the 2 nic from Intel i350 T2 card show up as eth0, 1.
a bit more detail:
My unraid manage port is one of the nic on that i350 T2 card, the onboard 2.5G nic port I use to directly connect to my PC for faster file transfer.
So without the 2.5G nic showing up in the network setting, my direct drive mapping connecting to my PC is gone, but I can still mange my unraid server with local lan.