When migrating virtual machines between cluster nodes, if the virtual networks are not correctly configured on all the cluster nodes, the virtual machines will end up in the Not Connected state when migrated. This is due to the new architecture of Hyper-V virtual networks. Virtual networks are uniquely identified by GUIDs. Therefore a virtual network across two Hyper-V hosts cannot have the same GUID defined for the virtual network.
When a virtual machine is started, it checks the GUID of the virtual network defined in the xml configuration file. If the GUID is not found, the name of the virtual machine is checked. If there is a virtual network name that matches, the virtual machine will be connected to that virtual network. If neither matches, the virtual machine is not connected to any virtual network.
The trick is that the virtual networks have to be named exactly the same across the nodes. That means that the case and spelling needs to be the same. To help ensure that the case is the same, it is a good idea to either standardize on all upper or all lower case when typing in the virtual network names.
