I have a Server 2012 Standard R2 Dell T610 Server that is brand new that has 2 on board NICs. THe server will stay connected to the network for a couple days (2-3) and then will disconnect. The connection always shows as an X as if it is not physically connected to the switch. I can disable and enable the interface (either one) and it immediately connects back to the network. I have even installed a PCIe Gigabit NIC which has yielded the same symptoms. I have to believe it is an issue with Windows; however, I have never seen this behavior before. Any help is greatly appreciated!