i have seen environments running Oracle RAC HB network over NSX overlay segments. It is not an issue at all.
- For some environments we have kept it as dedicated isolated L2 segment to ensure no other VM can reach it. In NSX DFW this L2 segment is open (allow any any and apply to this segment only).
- Some other have kept the network as routed but used NSX DFW to block unwanted access. A dedicated security group for Oracle RAC VMs is created and all traffic sourced and destined to security group is allowed, any other is blocked by implicit deny. (SG-Oracle to SG-Oracle -> Allow and apply to security group),
Overall in both scenarios there is no performance impact to Heartbeat network.
Thank you so much for your feedback, I'll explain it to them and I will keep you informed if it works without problem.