http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1013013

You experience these symptoms:
  • In vCenter 4.0, VMware HA might not failover virtual machines when a host failure occurs.
  • When the ESX host’s IP address in a VMware HA enabled cluster is configured with certain IP addresses, the node failure detection algorithm fails.
  • You are susceptible to this issue when all of your Service Console Port(s) or Management Network IP address(s) on your ESX host fall within the following range:

    3.x.x.x – 9.x.x.x
    26.x.x.x – 99.x.x.x

Note: You are not affected if one of Service Console Port(s) or Management Network IP address(s) on your ESX host falls outside of this range.

vCenter 4.0 patch 1 will help to fix this issue.

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