Other network connections are disabled after you disable one network adapter in Device Manager in Windows Server 2012 R2

Applies to: Windows Server 2012 R2 DatacenterWindows Server 2012 R2 StandardWindows Server 2012 R2 Essentials More

Symptoms


Consider the following scenario:
  • You have a computer that's running Windows Server 2012 R2.
  • The computer has one physical network adapter, which in turn has two or more ports. Therefore, you can see multiple logical network adapters in Device Manager.
  • You disable one network adapter in Device Manager and then restart the computer.
In this scenario, the other network connections are also displayed as disabled.

Cause


The physical network adapter is an PCI-E device that supports Alternative RID Interpretation (ARI). The logical network adapter you have disabled is at the function 0 port of the physical network adapter.

More information


Note Microsoft recommends that you don't disable a network adapter at the function 0 port. 


When a computer starts, Windows reads the hardware MaxPayLoadSize settings from hardware registry settings. 

Then, Windows calculates an optimized MaxPayLoadSize value for the PCI-E bus and the endpoint devices on this bus. In this situation, Windows chooses a maximum value that's supported by both the bus and the endpoint devices. (If MaxPayLoadSize of the bus is lower than the maximum MaxPayLoadSize value of the endpoint devices, Windows will choose the MaxPayLoadSize of the bus.)


Later, when Windows starts the bus and the endpoint devices, the optimized setting will be written into hardware registry settings for the bus and the endpoint devices.

When the function 0 port is disabled, Windows will not start the device at function 0. Therefore, the operating system cannot write the MaxPayLoadSize setting back to the function 0 device. Although the operating system does write the setting to function 1 or other ports, if the endpoint device is a ARI device, the MaxPayLoadSize setting on function 1 or other ports is ignored.

Therefore, the bus has the optimized setting, whereas the endpoint devices still have the default setting. This may trigger mismatched MaxPayLoadSize values between the bus and the endpoint devices.

When the endpoint devices are network adapters, the mismatched MaxPayLoadSize settings will break network controller driver functions and disable all network connections.

Status


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.