Flash VM Boot
ESX/ESXi hosts enable binding the software iSCSI adapter (HBA) to VM Kernel network(s). If such a binding is configured for an ESX/ESXi host that is used as a target for Flash VM Boot, the connectivity between the host and the Transporter might not be available at the iSCSI layer.
If an iSCSI binding is configured for a host which you plan to use as a target for Flash VM Boot, verify or configure the connectivity at the iSCSI layer (either by selecting a host without binding, removing binding on a host, or adding dedicated VM Kernel network to the binding that allows the connectivity).