To upgrade vCenter Server and ESXi instances, your systems must meet specific requirements. vCenter Server Upgrade CompatibilityThe upgrade to vCenter Server 6.0 affects other software components of the data center. vCenter Server for Windows RequirementsTo upgrade vCenter Server on a Windows virtual machine or physical server, your system must meet specific hardware and software requirements. vCenter Server Appliance RequirementsYou can upgrade the vCenter Server Appliance on an ESXi host 5.0 or later. Your system must also meet specific software and hardware requirements. Required Ports for vCenter Server and Platform Services Controller The vCenter Server system both on Windows and in the appliance, must be able to send data to every managed host and receive data from the vSphere Web Client and the Platform Services Controller services. To enable migration and provisioning activities between managed hosts, the source and destination hosts must be able to receive data from each other. vCenter Server Database Configuration NotesAfter you select a supported database type, make sure you understand any special configuration requirements. ESXi RequirementsTo install ESXi 6.0 or upgrade to ESXi 6.0, your system must meet specific hardware and software requirements. vSphere DNS RequirementsYou install or upgrade vCenter Server, like any other network server, on a host machine with a fixed IP address and well-known DNS name, so that clients can reliably access the service. vSphere Web Client Software RequirementsMake sure that your browser supports the vSphere Web Client. Client Integration Plug-In Software RequirementsIf you plan to install the Client Integration Plug-in separately from the vSphere Web Client so that you can connect to an ESXi host and deploy or upgrade the vCenter Server Appliance, make sure that your browser supports the Client Integration Plug-in. vSphere Client RequirementsYou can install the vSphere Client to manage single ESXi host. The Windows system on which you install the vSphere Client must meet specific hardware and software requirements. Required Free Space for System LoggingIf you used Auto Deploy to install your ESXi 6.0 host, or if you set up a log directory separate from the default location in a scratch directory on the VMFS volume, you might need to change your current log size and rotation settings to ensure that enough space is available for system logging .