With the VMware Host Client, you can manage single ESXi hosts during vCenter Server upgrades or when vCenter Server stops responding or becomes unavailable.
The VMware Host Client has a crucial set of troubleshooting functions, which allow you to perform tasks on the ESXi host that you are logged in to if vCenter Server is unavailable. These functions include but are not limited to configuring advanced host settings, licensing, managing certificates, using the ESXi Shell, enabling Lockdown mode, and so on.