When you try to install Update Rollup 2 for Microsoft Exchange Server 2010 Service Pack 3 (KB2866475), you receive the following error message:
The feature you are trying to use is on a network resource that is unavailable.
Click OK to try again, or enter an alternate path to a folder containing the installation package 'ExchangeServer.msi' in the box below.
To work around issue, click the Browse button in the dialog box, locate the ExchangeServer.msi file, and then click OK to continue the installation. The ExchangeServer.msi file is located on the Exchange Server 2010 installation media.