TIP: RPC issues with VirtualBox #VirtualGeek

I recently had occasion to set up Virtual Machine Management features of a Windows server hosted within a VirtualBox-based VM instance. I'd done this in the past but this time I was connecting to target VMs hosted within a Windows failover cluster. I could see the clustered VMs just fine (via the Failover Cluster Manager) but when selecting a specific VM and clicking "Manage virtual machine" my VMM console spat out a "RPC server unavailable" error.

It turns out that VirtualBox does not pass through the needed RPC traffic when the VirtualBox-hosted machine's NIC is in "NAT" mode.  If you encounter this, switching the NIC from the default "NAT" to "Bridged Adapter" may take care of the problem (as it did for me).