AZ-802: Administering Windows Server

Nested virtualization requires the physical host's processor virtualization extensions to be passed through to the guest so that VM1 can itself install and run the Hyper-V role and host virtual processors for its own child VMs; this is accomplished by exposing virtualization extensions on VM1's virtual processor configuration, which is a prerequisite before the Hyper-V feature can even be installed inside a virtual machine. Separately, a Hyper-V virtual switch port normally forwards frames only for the single MAC address it has learned belongs to a given virtual network adapter, so traffic originating from VM1's nested virtual machines — which present their own, different MAC addresses — would be dropped by VM1's external virtual switch connection. Enabling MAC address spoofing on VM1's network adapter allows frames carrying source MAC addresses other than the adapter's own assigned address to pass through the switch port, which is what lets the nested virtual machines' traffic reach, and be reached from, the physical LAN.