When planning your next VMware ESX server installation that will be managed by VirtualCenter 2.5, make sure you provision for redundant networking for the ESX service console port. VirtualCenter 2.5 gives you a warning if you only have one interface assigned as the role of service console port, but earlier versions of VirtualCenter did not give this message. It is recommended, but not required, to have redundant networking for the service console port. If you only have one interface assigned, VirtualCenter will display the following indicator on the cluster:
Protect against hiding other errors
If (like me) you upgraded to VirtualCenter 2.5 and had only one interface assigned for the service console port role, this error will remain present on your cluster indefinitely. This is only a warning, but the problem with this situation is that should a new error arise, you would not know because the indicator on the cluster is always displayed and you would not notice it as new. I had this happen on ESX 3.01 and 3.02 hosts. I expect 3.5 hosts to behave in the same fashion.
If you have recently upgraded to VirtualCenter 2.5 and now have this error message displaying, one thing you can consider doing is taking one of your interfaces from a teamed vswitch for a virtual machine network that does not need redundancy (like a test network) and reconfiguring it on the network and within VirtualCenter to be on the same network as the service console port. Once it is available, bring it in as a standby member to clear the warning.