You upgrade the vSphere Replication appliance and any additional vSphere Replication servers by using a downloaded ISO image.
The downloadable ISO image is the only means of upgrading from vSphere Replication 5.5.1 or 5.8 to vSphere Replication 6.0. You cannot upgrade vSphere Replication from version 5.5.1 or 5.8 to version 6.0 by using vSphere Update Manager or the virtual appliance management interface (VAMI) of the vSphere Replication appliance. After you have installed vSphere Replication 6.0 or upgraded to version 6.0 by using the ISO image, you can use the VAMI or Update Manager to install later 6.0.x update releases.
You cannot downgrade to an earlier version of vSphere Replication.
vSphere Replication Upgrade Scenarios
You use the ISO file to upgrade to a major version of vSphere Replication, for example from 5.5.1 to 6.0.
You use Update Manager, the VAMI, or the ISO file to install an update release of vSphere Replication, for example upgrade 5.5.0 to 5.5.1.
These examples of upgrade and update scenarios are not exhaustive. For the full list of supported upgrade paths, see the Compatibility Matrixes for vSphere Replication 6.0 at https://www.vmware.com/support/vsphere-replication/doc/vsphere-replication-compat-matrix-6-0.html.
You can upgrade vSphere Replication 5.5.1 to 6.0 by using the ISO file for vSphere Replication 6.0.
You cannot upgrade vSphere Replication 5.5.1 to 6.0 by using Update Manager or the VAMI.
You can upgrade vSphere Replication 5.5.0 to 5.5.1 by using Update Manager, the VAMI, or the ISO file.