In the context of stretched clusters and BYON, we would like the installer to support the provisioning of OCP masters and workers on different subnets.

Right now, we only support machineSubnet platform parameter (for BYON) which will be used to put all machines (master & worker nodes) within the same subnet as a primary interface.

What we want is to provide a list of subnets that will be used to deploy the nodes. We would need a new machine pool parameter subnets (AWS already has this parameter).

e.g.

controlPlane:
  name: master
  platform:
    openstack:
      type: m1.xlarge
      zone:
      - az0
      - az1
      - az2
      subnets:
      - d778346a-e9a9-450c-9302-b3f41de4816a
      - 3d645a02-0a26-415b-8678-6e869af19875
      - c33f60d9-fa22-4ec5-ac33-bcc53291c3fb
   replicas: 3 

We need to clarify how we'll deal with the existing machineSubnet parameter.

Conditions of satisfaction:

• On day 1, using IPI, I can deploy 3 masters in 3 different subnets
• Validate that the number of subnets matches with the number of zones
• 100% backward compatible and machineSubnet remains available