A linked Mode allows us to log in to single vCenter server to view and manage the inventories of all the vCenter server systems in the same linked mode group. Linked mode groups can be configured during vCenter servers installation or after vCenter server is installed.vCenter server Linked mode uses Microsoft ADAM (Active directory Application Mode) to store and synchronized data across mutiple vCenter Server Systems. Each ADAM instance stores data  (including information about riles and licenses) from the vCenter server systems in the group. This information is replicated across all the ADAM instances in the group.vCenter server linked mode instances can share role definitions and licensing.

You can perform the below actions, when connected vCenter server systems in Linked Mode:

Linked in Simulatneously to all connected vCenter servers

Search and view the Inventories of all the vCenter systems connected in Linked mode group.

You cannot migrate Virtual machines between vCenter server systems connected in Linked mode.

Linked Mode Prerequisites

1. Operational DNS servers

2. Both the vCenter servers which are going to be joined by vCenter linked mode can be same domain or  in different domains but two-way domain trust relationship should be established between the domains.

3.vCenter linked mode installer should be run by the user who has administrative privilages in both the vCenter servers.

4.Time Synchronization between two vCenter servers should not exceed more than 5 minutes. Use network time synchrinization like NTP is recommended.

I have two vCenter servers on different versions (vCenter 4.0 & vCenter 4.1). As per Vmware, Vcenter server 4.0 and vCenter server 4.1 can be joined in the same linked mode group.You need both vSphere client 4.0 & 4.1 on the system to connect to that linked mode group.

Procedure

Since I have already installed both the vCenter servers, Please follow the below procedure to Join a liked Mode Group.

1. Goto Start > All Programs > VMware > vCenter Server Linked Mode Configuration.

2. Click on Next and Select “Modify linked mode configuration” and click Next. IF you want to modify the vCenter server linked mode configuration, select modify and click on Next.

3.There are two options:-

A.Join this vCenter Server instance to an existing linked mode group or another instance (For creating or Joining into Linked MOde Group)

B.Isolate this vCenter server instance from likned mode group (To isolate from Linked Mode Group)

Since we are creating Linked mode Group, select “Join this vCenter Server instance to an existing linked mode group or another instance” and click Next

4.Enter the Remote vCenter Fully Qualified domain name and Ldap port number to be part of this linked mode group and click on Next

5.If you want to review or change any of the settings, click Back. Click Cancel to Exit the wizard. We are sure about our settings, click on Continue to proceed with the installation.

6. Click on Finish. It will take few seconds to minutes depend on the size of your inventory.

After the installation completed, restart the vCenter server and Connect the vCenter Server using vSphere Client and You can see the both the vCenter server instances in a single vSphere Client login.

Thanks For Reading !!!!