What happens to virtual machines if vCenter Server becomes unreachable?

When the vCenter Server becomes unreachable, virtual machines (VMs) continue to run based on their last resource assignments. This means that the running state of the VM is not directly dependent on the vCenter Server's availability.

vCenter Server primarily functions as a management layer for the VMs and the underlying ESXi hosts. It handles tasks such as resource allocation, VM provisioning, and monitoring. However, once a VM is powered on and running, it operates independently of vCenter Server. The ESXi host continues to manage the VM according to the resources allocated and the settings defined prior to the vCenter becoming unreachable.

This behavior allows for a level of resilience and operational continuity, as virtual machines can keep processing tasks even if the vCenter loses connectivity. Once the connection is restored, administrative functions, such as VM management and monitoring, will be available again, but the VMs themselves will not experience an immediate interruption in their operation.

Other considerations about the remaining options include that the virtual machines do not stop functioning immediately, become inaccessible for management, or are permanently deleted merely due to vCenter Server being unreachable. The VMs will keep running as long as the underlying infrastructure remains intact and powered on.