Private interconnect for RAC

Dear Expects,

Please help me to clarify on the below:

We are planning to implement Oracle -12c RAC on Solaris Sparc Virtualization  environment.

Base Hardware : sparc T5-4

Six Logical domain will be created on top of the base hardware and three RAC cluster will be created on logical domain.

My sysadmin says that public and private network will shared across all the three RAC cluster.I have told him it's not recommended to share network.But my sysadmin is not ready to accept  he says that in virtualization resources can be shared.

Option :1

Ethernet for private Interconnect:

One public Ethernet network interfaces for three database.