An Azure virtual network can be selected when initiating a test failover. ASR attempts to create test VMs in a subnet with the same name and same IP address as that provided in the Compute and Network settings of the VM.
If a subnet with the same name isnt available in the Azure virtual network used for test failover, then the test VM is created in the first subnet alphabetically. If the same IP address isnt available in the subnet, then the VM receives another available IP address in the subnet.