If there are already virtual machines on the cluster that EVC needs to be enabled on then the issue will be that the cluster needs to be evacuated or I think the virtual machines turned off. EVC cannot be enabled on a a cluster with active servers.
If the VC is a virtual machine then have a look at this link http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1013111
I hope this helps you answer the question and if it does then please leave points.
- There is no downtime when you enable EVC
- you must enable vmotion on a vmkernel port in Networking
my advice is to use a dedicated vlan
For enabling EVC you dont want to down the VMs but to add the host in EVC cluster you have to power off the VMs and add it
EVC cluster will not allow to add the host or enable the feature on the power on VMs host