You can perform ESXi upgrades with custom images and async drivers. Upgrade ESXi with Custom ISOYou can upgrade ESXi with a custom ISO from your vendor. This feature is available for VMware Cloud Foundation version 3.5.1 and later. Upgrade ESXi with VMware Cloud Foundation Stock ISO and Async DriversYou can apply the stock ESXi upgrade bundle with specified async drivers. This feature is available for VMware Cloud Foundation version 3.5.1 and later.