Hyper-V requires at least one virtual switch (vSwitch). The vSwitch is a software-based layer-2 Ethernet switch. Depending on your requirements, you may have more than one vSwitch. Depending on how the vSwitch is configured, it can be allowed to talk to physical networks, just the VMs on the host, or VMs only. Each virtual network adapter (vNIC) configured on a VM is assigned to a vSwitch. An example is shown in Figure 2.
Figure 2. Virtual Switch Manager
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For more information, see the Microsoft Learn article “Plan for Hyper-V networking in Windows Server”.