Adding ESX 3.5 Servers to vCenter 4.0

I came across this today while performing and migration from vCenter 2.5 to vCenter 4.0

When adding an ESX 3.5 Server you will need to provide a license for the host.

vCenter 2.5 uses a separate application (FLEXLM) and there is no way to point the ESX host to use a vCenter 4.0 License.

From the vSphere Upgrade Guide

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So all of this is pointing to the same thing - you have to connect your vCenter server to the old licensing server.

So how do you do this?

In the vSphere Client, select Home > vCenter Server Settings > Licensing and add your old licensing server in the field at the bottom.

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Once the ESX servers have been upgraded then you will be able to assign the licenses from your vCenter 4.0 Server and remove the licensing server.