A program that lets virtual machines transfer data to one another, directing traffic based on media access control (MAC) addresses. Virtual switches are usually installed with software but can also be embedded in the server’s firmware.
External virtual switches are bound to the host machine’s physical network card and let VMs access the physical network that the host is connected to.
Internal virtual switches normally only allow traffic between VMs and the host itself. As of 2016, however, they can also access physical networks via NAT forwarding.
Private virtual switches only allow communications between virtual machines.