ESX host continually disconnects from vCenter following ESX 4 Upgrade

I ran into this after I upgraded my vCenter to 4.0, so I thought I would share. KB 1011647

• “KB Article: 1011647
• Updated: Jun 12, 2009

Symptoms

• You upgraded your VirtualCenter instance to vCenter 4.x
• You upgraded ESX hosts to ESX 4.x
• Your ESX disconnect within a couple of seconds of being connected added to vCenter
• Upon reconnect, host disconnects again within 30 seconds 
• ESX 3.5 hosts remain connected in VirtualCenter
• ESX not responding after upgrade to ESX 4

Resolution

This issue occurs if you have recently upgraded to ESX 4.0 and vCenter 4.0.

This can occur if vCenter incorrectly pushed the loopback IP address to the vCenter agent configuration. This can be verified by opening the /etc/opt/vmware/vpxa/vpxa.cfg on the ESX 4 host and checking to see if <serverIp> contains 127.0.0.1.

To resolve the issue, in vCenter:

1. Click Administration > vCenter Server Settings.
2. Click Runtime Settings.
3. Under Managed IP address, type the IP of the vCenter Server.
4. Connect the ESX host. It now remains connected. “

Source Post. http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1011647

Worked for me, hope this helps someone in the future.