A vSphere upgrade will require careful assessment of the existing infrastructure. You will need to ensure that the server hardware is compatible with ESXi 6.5. If the existing infrastructure has vCenter components on Microsoft Windows, then you will need to verify whether the current Windows Servers versions are supported for the installation of vCenter 6.5 and its components. If the existing environment has other third layer components, such as the VMware NSX, vRealize Automation, vRealize Operations Manager, vCenter Site Recovery Manager, then it becomes essential to verify whether upgrading the core vSphere components will leave the third layer components unsupported/incompatible. In this section of the chapter, you will learn how to check the hardware compatibility of the existing server hardware, check Windows Server operating system compatibility with the vSphere 6.5 components, and verify third layer product interoperability with the core vSphere 6.5 management components. We will also review various upgrade paths available based on the existing vSphere environment's version and deployment models.