Prepare the vCenter Server system for joining a Linked Mode group.
Before joining a vCenter Server to a Linked Mode group, review Linked Mode Considerations for vCenter Server.
All the requirements for standalone vCenter Server systems apply to Linked Mode systems.
The following requirements apply to each vCenter Server system that is a member of a Linked Mode group:
vCenter Server does not support Linked Mode groups that contain both version 5.x and pre-5.0 versions of vCenter Server. Similarly, vCenter Server does not support Linked Mode groups that contain different 5.x versions of vCenter Server or different versions of vCenter Single Sign-On. After all 5.x vCenter Server and vCenter Single Sign-On instances in a Linked Mode group are upgraded to the same 5.x version, you can rejoin them.
Make sure that all vCenter Servers in a Linked Mode group are registered to the same vCenter Single Sign-On server.
To join a vCenter Server to another vCenter Server in Linked Mode, the currently logged-in user who is performing the join operation must have access to the vCenter Server database of each vCenter Server.
When you join a vCenter Server instance to a Linked Mode group, the installer must be run by a domain user who is an administrator on both the machine where vCenter Server is installed and the target machine of the Linked Mode group.
When you join a vCenter Server instance to a Linked Mode group, if User Account Control (UAC) is enabled on the machine, the join operation requires elevated privileges through the Run as administrator option. This is true even if the logged-in user is a domain administrator user.
To join a Linked Mode group the vCenter Server must be in evaluation mode or licensed as a Standard edition. vCenter Server Foundation and vCenter Server Essentials editions do not support Linked Mode.
DNS must be operational for Linked Mode replication to work.
The vCenter Server instances in a Linked Mode group can be in different domains if the domains have a two-way trust relationship. Each domain must trust the other domains on which vCenter Server instances are installed.
All vCenter Server instances must have network time synchronization. The vCenter Server installer validates that the machine clocks are not more than five minutes apart. See Synchronizing Clocks on the vSphere Network.