I have two ESXi 4.1 hosts setup in my test environment. The vCenter and the SQL Server hosting the vCenter database are setup as two separate virtual machines in the test environment. We have a power maintenance and I shutdown all the virtual machines and the two ESXi 4.1 hosts.
After the maintenance, I powered up the ESXi 4.1 hosts. Using vSphere client, I connected to the ESXi hosts to power the SQL Server virtual machine first then followed by the vCenter virtual machine. After the vCenter has powered up, I tried to connect to the vCenter via vSphere client but failed. Then I noticed that the vCenter services were not able to start and the vCenter was not able to communicate with the SQL Server.
I took a look at the virtual machine properties and saw that the Network adapter was showing Invalid backing. The warning message said that the host does not have any virtual machine network.
Okay, I have configured the virtual machines to use the virtual machine network on a Virtual Distributed Switch (vDS) but the vDS information was not loaded.
The problem is I need to get the vCenter up to get the vDS back. But the vCenter cannot start because it cannot access the database because there is no network connectivity. Sounds like an infinite loop of dependency. To workaround this, I created a temporary virtual machine network using the virtual standard switch on each host. Configured the virtual machines to use the temporary virtual machine network.
This allowed the vCenter to resume communication with the SQL Server and start up vCenter. Once this was fixed, the vDS came back.
After the vDS is back, I re-configured the virtual machines to use back the virtual machine network on the vDS.
This problem does not seem to exist in ESXi 5.x.