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

In general, it is best practice to migrate virtual machines on an extended network to keep a VM’s IP address, MAC address, and overall identity. But this is not always the case, and in some scenarios it might 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 customizations are selected under Edit Extended Options in the Migration interface. To make Guest OS IP address changes, expand the NIC entry listed below the Extended Options.

Guest Customization is applied during the switchover phase when the virtual machine is powered on.

This functionality is also supported for reverse migrations.


When changing Guest OS information, the original settings are not stored by HCX.

For additional details about 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.