R420 vflash boot

Hi there,I've got:

Dell PE R420 Server

SD card formated and initialized = vflash

When I'm shutting down server and booting up it again, it won't boot because can't get a boot media, it's trying to scan hdd, floppy, dvd,network but don't even try vflash. To boot from vflash (i've got esxi5.1 server on it), I must do this:

open web idrac7 and login in to it. Select vflash, attach media, check the checkbox in 'attach' - reboot my server.

Think it's not right, mb there's a better way how can I automate booting my server from vflash drive?