This blog post covers two main methods for a VMware ESXi upgrade: Follow this vSphere upgrade order, otherwise you can lose the connection between an ESXi host and vCenter. If you need to update ESXi to ESXi 7.0 Update 2 in vCenter, you need to update vCenter or deploy vCenter 7.0 Update 2 first. Thus, you have to upgrade vCenter first and only then proceed to the ESXi upgrade if you want to upgrade vSphere 6.7 to 7.0. VMware vCenter 7.0 can manage ESXi 7.0, ESXi 6.7 and ESXi 6.5, but vCenter 6.7 cannot manage ESXi 7.0 hosts.
If an unsupported device is present, such as an old unsupported CPU or disk controller, the ESXi upgrade will not be applied to the server. The hardware of the server running ESXi 6.7 must be compatible with ESXi 7.0, that is, it must meet the hardware requirements for ESXi 7.0.DISCOVER SOLUTION ESXi Upgrade Requirements
