Unable to add an Availability-Zone in Multi-Zone cluster after the cluster is created

Solution Verified - Updated -

Environment

  • Red Hat OpenShift Service on AWS (ROSA)
    • 4

Issue

  • Is it possible to add an Availability-Zone (AZ) in Multi-Zone cluster after the cluster is created using machine pool.
  • Can we add more than 3 AZ's while creating cluster.

Resolution

  • If Cluster is not a byo-VPC cluster, then the AZ's selected during install-time are the only ones that can be used. It is possible to add AZ after the creation of cluster only if it is a byo-VPC cluster, and subnetting is accounted for.

  • Without byo-VPC, when ROSA creates the VPC, it chops the VPC into equal subnets and assumes AZ's to the subnets , so there's no more addresses in the VPC to apply to AZ's at that point.

  • It is not possible to add more than 3 AZ's while creating cluster if it's not a byo-VPC cluster and should be using byo-VPC to resolve it.

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