To select a suitable reference host, vCenter Server performs complex version and compatibility checks on the target host.

Starting with vSphere 7.0 Update 3, a major-version vCenter Server instance can manage hosts of all ESXi Update release versions within the respective major version. For example, a vCenter Server 7.0 Update 3 instance can manage ESXi hosts and hosts profiles of version 7.0 GA, 7.0 Update 1, 7.0 Update 2, and 7.0 Update 3. This change affects the reference host selection for particular host profile operations.

Version Check

To select a reference host, vCenter Server checks whether the target host is of the same ESXi Update release version as the host profile. For some operations, the target host can run a later ESXi version than the ESXi version of the host profile. For example, if you want to edit a 7.0 Update 3 host profile, the reference host that validates the host profile cannot be running ESXi 7.0 GA, 7.0 Update 1, or 7.0 Update 2.

Compatibility Check

In addition to checking the version on the target host, vCenter Server performs an extensive compatibility check that includes a subprofile compatibility check in the existing releases. Starting with vSphere 7.0 Update 3, to appoint a reference host, vCenter Server checks the advanced options and the default roles in the target host. A reference host must support the advanced options of the host profile it validates. Also, the default roles in the reference host must match the default roles in the host profile.

Host Profile Operations and Required Reference Host Versions

A reference host is needed to validate the host profile during different host profile operations and workflows. Starting with vSphere 7.0 Update 3, depending on the operation, the reference host must be of exactly the same or later Update release version as the host profile it validates. The following table summarizes the compatible reference host versions for different host profile operations if your environment runs a vCenter Server instance 7.0 Update 3 or later.
Host Profile Operation Compatible Reference Host Version
Edit The same Update release version as the host profile.
Check Compliance The same or later Update release version as the host profile.
Remediation The same or later Update release version as the host profile.
Attach The same or later version as the host profile.
Import/Export The exact same version as the host profile.
Note: If the vCenter Server instance is of version earlier than 7.0 Update 3, Update release versions are not checked during the selection of a reference host. vCenter Server only checks if the reference host and the host profile are of the same major release version, for example 6.x or 7.x.