Before you begin, you will need to install and configure a TFTP server for PXE booting ESXi hosts. Read the Configuring the Trivial File Transfer
Protocol (TFTP) server for an ESXi PXE boot environment recipe. Also, make a note of the BIOS DHCP file name from the Auto Deploy Runtime Summary. As of vCenter 6.7, it is undionly.kpxe.vmware-hardwired.