One characteristic of Bulk Migration is the ability to customize several aspects of the Guest OS.

In general, it is best practice when migrating virtual machines on an extended network to keep a virtual machine's IP address, MAC address, and overall identity. In some scenarios, it can be beneficial to modify a VM’s characteristics. For example, it might be necessary to migrate non-production workloads to free up private network prefixes, and making these changes during the migration can save the effort of manually updating the VM settings after the migration. The following guest customizations are available:

  • Guest OS Hostname
  • IP Address
  • Gateway
  • Netmask (Subnet Mask)
  • Primary DNS
  • Secondary DNS
  • Security Identifier (Windows SID)
  • Run Pre- or Post-Guest Customization scripts

Guest customization is available only for specific guest OS types. See Guest OS Types for Guest Customization.

You select guest customizations using the Edit Extended Options in the Migration interface. Certain customization options only appear when you select the Edit Extended Options on a virtual machine level.


HCX applies the guest customization options during the switchover phase when the virtual machine is powered on.

This functionality is also supported for reverse migrations.


When changing Guest OS information, HCX does not store the original settings.

All values must be specified in the wizard, even those that must remain unchanged.

Values will be cleared on the migrated virtual machine for fields left empty if IP Customization is configured.

For details about the Extended Options available for Bulk migration, see Additional Migration Settings.


Changing the Security Identifier of a Windows machine that is already the member of a Windows domain breaks the domain relationship and requires the machine to be re-joined. On a domain controller, this operation can impact the domain. By default, the Generate New Security Identifier (SID) option is not selected.