(i know work with 9.6 sp1)
if you have prefered server :
1- create a ldmain share for the replication
\\preferedserver\ldmain
2- create a landesk share:
\\preferedserver\landesk on your ldmain directory :
configure replication for \\ldms\ldmain\landesk\vboot
after it create in your provisioning a vboot option with prefered server :
execute it on a devices and see currentdownload.log :
landeks will replace http by unc for the download of boot file. no need specialy to have an iis.
after devices reboot on boot.wim.