Hi! I (and not only me) wrote about this error 3 months ago. There was no response. I recorded a video about this error. This is a critical error.
Error description - After POWER OFF and then POWER ON VM - is automatically added the new network interface.
Open Opennebula. Create new VM. Add Network and deploy.
See in vCenter - VM is deployed and work.
Return to Opennebula and POWER OFF VM.
POWER ON VM
Go to vCenter and we see our VM with MAC conflict and 2 NICs.
It has already been solved for future releases but if you want to solve your issue, visit the ticket and try to change that line in the vcenter_driver.rb file. It seems that in some situations that line didnāt work as expected and a new NIC with same MAC was created.