Guest NICs disconnected after upgrade

We are upgrading our infrastructure to ESXi 4.1 and had an unexpected result in Development cluster where multiple VMs were suddenly disconnected after vMotion. It sounded a lot like a problem that I had seen before where a misconfiguration in the number of ports on a vSwitch prevents vMotioned VMs from being able to connect to the switch. If a vSwitch has too few available ports, the VMs that vMotion over are unable to connect to the switch. You generally avoid this with host profiles, but it’s possible a host in the Dev cluster fell out of sync. In any event, the server that was being upgraded this evening had been rebuilt and it wasn’t worth trying to figure out what the configuration might have been. I needed to go through, find all VMs that should have been connected but weren’t, and reconnect them. I decided that I needed:

• VMs that were currently Powered On – obviously as Powered Off VMs are all disconnected
• VMs with NICs currently set to “Connect at Power On” so I could avoid connecting something that an admin had intentionally left disconnected
• VMs with NICs currently not connected

Note that this script will change network settings and REBOOT VMs if you execute it. I was watching the script while it executed, I pinged the guest DNS name first to ensure the IP wasn’t already on the network, then connected the NIC, then pinged again to make sure it was back on the network. I figured I could Control-C to stop if something looked wrong. I rebooted all of the guests to avoid any failed service / failed task problems that might have occurred while the guests were disconnected.

$vms=get-cluster "Development" | get-vm | Where { $_.PowerState -eq "PoweredOn" }| Sort-Object Name
foreach ($vm in $vms)
{
   $nics = $vm | get-networkadapter | Where {$_.ConnectionState.Connected -eq $false -and $_.ConnectionState.StartConnected -eq $true}
   if ($nics -ne $null)
   {
  	 foreach ( $nic in $nics )
  	 {
	     	write-host $vm.Name
	     	write-host $nic
	      	ping $vm.Guest.HostName -n 5
		$nic | Set-NetworkAdapter -Connected $true -confirm:$false
	 }
 
        ping $vm.Guest.HostName -n 5
	$vm | Restart-VMGuest
 
   }