Shutdown of VM while network connection lost

Hi,

I found, any time the network connection lost of my ESX 4.1.0 Server, all virtual maschines shut down.

One NIC (nic0) is linked on vSwitch0 with VM Network & Service Console the 2nd NIC (nic1) is linked to vSwitch1 with VM Kernel.

The shutdown only happes in case nic0 lost network connection.

My question: How can I disable this behavior?