Since Update Manager is configured and operated from the vCenter layer, it can be used to upgrade ESXi hosts across different clusters. This means that you can create more than one upgrade baseline for use with the various hosts/clusters. These baselines, for self-evident reasons, are formed using different ESXi images. However, the important thing to keep in mind is that Update Manager cannot be used to create upgrade baselines that are older than its current major version. In our case, this means we cannot use Update Manager 6.7 to create ESXi 6.5 upgrade baselines. It would not allow you to import ESXi 6.5 images into the Update Manager cache.