VMware vSphere: Both Reprotect and Failback require a site-to-site VPN to replicate data to the on-premises datacenter. ASR Reprotect assumes that the on-premises datacenter is up and running and is ready to receive the replication data from Azure.

Azure IaaS: Azure VMs can be reprotected after failover, so that data replicates back from the secondary to the primary Azure region.

Reprotect does not apply to Hyper-V VMs and Physical machines.

UR40 introduces the following enhancement: Machines in the DR region are now cleaned up automatically after failback is complete and when the VMs are re-protected. There is no need to manually delete VMs and NICs.