To help ensure a successful upgrade to vCenter Server 4.0 or later, it is important that you diagnose and fix any potential problems on the managed ESX/ESXi hosts.

Software called vCenter Agent runs on all managed ESX/ESXi hosts. This software coordinates actions received from vCenter Server. When you add a host to vCenter Server, the agent is installed on the physical ESX/ESXi host. When you upgrade to vCenter Server 4.0, the agent residing on each ESX/ESXi host must be upgraded as well.

During a vCenter Server upgrade, the existing agent software is uninstalled and the updated agent software is installed in its place. If the upgrade fails, the updated agent software might not be installed and the host might become unreachable by VirtualCenter 2.x and by vCenter Server 4.0. To avoid this condition, you can run the vCenter Agent Preupgrade Check tool before you attempt to upgrade to vCenter Server 4.0.

The vCenter Agent Preupgrade Check tool checks to make sure that the agent software is ready to be upgraded. Some of the checks include checking to make sure that the host is reachable, the disk space is sufficient, the network is functioning, the filesystem is intact, and required patches are applied. Each time you run the tool, the system queries and downloads any new updates for the tool. This action ensures that as new upgrade issues are discovered, the tool remains as useful as possible.


A successful vCenter Agent preupgrade check does not guarantee a successful upgrade to vCenter Server 4.0 or later. An upgrade to vCenter Server involves multiple components, and the tool checks only one component: the vCenter Agent. Also, the tool checks only known issues. Other issues might be present that the tool does not check.

The vCenter Agent Preupgrade Check tool is a diagnostic read-only tool that produces a report showing known issues that might prevent a successful upgrade of the vCenter Agent software. The tool does not fix the reported issues. You must resolve the reported issues manually and rerun the tool to verify that the issues are resolved.

Before you run the vCenter Agent Preupgrade Check tool, make sure the following prerequisites are met:

VirtualCenter 2.x must be installed on a Windows machine that is supported by vCenter Server 4.0.

The VirtualCenter 2.x machine must have a DSN configured that is compatible with vCenter Server 4.0.

The VirtualCenter 2.x database must be supported by vCenter Server 4.0. This means that, if needed, the database must be upgraded to work with vCenter Server 4.0. The MSDE database was supported in experimental mode in VirtualCenter Server 2.0.x, but is not supported in vCenter Server 4.0. The vCenter Agent Preupgrade Check tool will not detect the database. Upgrade to a supported database before using the tool. See Database Scenarios.

The ESX/ESXi hosts must be managed by VirtualCenter 2.x.

VirtualCenter Agent software must be running on each managed ESX/ESXi host.

Microsoft .NET Framework Version 2.0 must be installed on the VirtualCenter 2.x system.

VMware recommends that you have Internet connectivity from the VirtualCenter 2.x system. This allows new updates to be applied to the tool and allows you to view the reports and the Knowledge Base (KB) articles associated with the reports.


On the VirtualCenter 2.x system, download the vCenter Server 4.0 installation package or insert the vCenter Server 4.0 installation DVD.


Start the Preupgrade Check tool.

In the installation package or on the DVD, navigate to \vpx\agentupgradecheck and run the AgentUpgradeChecker.exe executable file.

Start the installation process from the DVD and when asked to select an item to install, select the Agent Pre-upgrade Check option from the Utility list.


Select the VirtualCenter 2.x DSN and select the login credentials that are appropriate for your DSN.

If you are not sure which credential type to select, check which authentication type is configured for the DSN (Control Panel > Administrative Tools > ODBC Data Sources > System DSN).


If the DSN requires a login for the credential type in use, enter a username and password and click Next.


Select a mode.



Scan all of the hosts

Select Standard Mode and click Next.

Specify hosts to scan


Select Custom Mode and click Next.


Select the hosts to scan and click Next.

To select all hosts in a cluster, double-click the cluster.


Click Run Precheck.

The tool takes 30-40 seconds for each host. When the check is complete, click Next.


View the pre-upgrade reports.

To view the report for an individual host, click the link next to the host name.

To view a summary report for all hosts, click View Report.

You now have a list of issues to resolve before you upgrade to vCenter Server 4.0.

From the report, use the linked KB articles to research and resolve the issues on each host. After you resolve the issues, rerun the vCenter Agent Preupgrade Check tool. Repeat this process until you resolve all the reported issues, and then proceed with your upgrade to vCenter Server 4.0 or later.