How vCentre communicates in BOTH Machines..
Vcentre communicates similarly in both machines.
1. when you add host to vcentre, vxpa process is run on host systems.
2. vpxa is used as interface between vcentre and host.
3. command send to host from vcentre(create new VM, Migrate, Edit VM) are run by hostd process which is aware of inventory available on that host.