If you encounter network connectivity (i.e disconnection) problems while attaching an external virtual network switch (I've encountered the error on an Intel 82579LM switch with all the latest updates available from both Microsoft and Lenovo installed), try this very simple trick (before you eventually run into manaul reconfiguration trap) - delete the network adapter from the device manager panel, then simply reinstall it and add a virtual switch again.

(Driver details can be seen below)