I am setting up recovery plans for disaster recovery between our two clusters. I have been through the documentation multiple times, and I still am confused by the test failover/failback subnets that are configured as part of the recovery plan.
Production is easy. We have the primary cluster in one location in Subnet A. We have a recovery cluster in another location in Subnet B. I just set the production subnets to be Subnet A and B at each location respectively with their matching gateway and prefix.
The Test Failover/Failback subnets continue to confuse me. The documentation indicates they should be isolated and non-routable subnets which makes sense. But WHERE are those subnets defined?
We use external IPAM. Each cluster is connected to a core switch stack at its location. We have a few different subnets/VLANs defined on those core switches, with a defined IP range, /24 in each case. All VMs have static IP addresses, though the core switches do run DHCP for each subnet.
We also have corresponding subnets/VLANs on the clusters, but they don't have IP ranges because that's handled by the core switches. Do I have create new "test" subnets on the core switches with VLAN IDs and IP ranges of their own, call them Subnet C and D? And those IP ranges and VLAN IDs I then create on the clusters, and use that as the Test Failover/Failback subnet in each location?
Where do Subnets C & D "live" is the question I can't grasp. I find conflicting information on whether or not I need to create actual dedicated subnets on the core switches, or if I don’t. Whether the subnet needs to be different for Test Failover/Failback. Whether the gateway IP/prefix should be different or the same as production.
I am quite sure this is much simpler than I am making it. But if someone could help me fully understand this, I would be deeply grateful.
Thanks!