@Vimal K Below is the response I got from our internal team:
You can't move an AKS cluster across RG. [Not Supported] You can rebuild the AKS cluster in the same RG as VMs but the infra RG for AKS is going to be different. And in any case RG does not matter. Look at N/W. Are the VMs and the AKS worker nodes in the same N/W? If so they can directly access, else peer the AKS Vnet with the VM Vnet. If peering is not possible due to subnet overlap and if you are using AKS with multiple nodepool support (VMSS node pool type basically) then
1) You can add another subnet in the AKS VNet (which does not overlap with the subnet CIDR of VMs) -> Add a new system mode node pool on AKS associated with the new subnet -> Drain earlier node pool and remove it -> peer new subnet in AKS Vnet with VM Subnet.
2) You can create new subnet in the VM Vnet -> create a new system mode node pool on AKS associated with the newly created subnet -> Drain the old node pool and delete it. In this case since both AKS node pool subnet and VM subnet are in the same VNet, communication over private IPs should not be a problem.
Hope it helps!!!
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