Searching through the messages in this forum i ran across my exact same

"I am looking to set multicasting sessions for mass imaging using a
Master/Client setup. I am having trouble getting the participants to
join the session based on RULES. Workstions do not even download the
boot files from pxe server. Multicasting sessions are successful when
participants are set to join based on existing workstation objects.

My assumption is that wether the workstations is imported or not, based
on the multicasting RULES, the workstations (if they meet the rules
requirements) should join the session. Correct?"

The answer was this:

nope... if they are imported they will use the wks object only.. if they
are not imported they will use the rules..

Here is my situation:

I'm somewhat new to the multicasting part of zen imaging....and this is
my first large multicasting project for already imported machines. I
work for a school system and I have a variety of about 7 different major
models of machines.....I have separate images setup for each of these
models....and during summer vacation I always go through all my
classrooms and reimage all the machines. My workstations are named by
classroom number in the order they are in the room...example D7_1, D7_2.
Well the 1st one might be one model and the 2nd a different one. What I
had in mind was to setup a different session for each model and base
rules accordingly for participation....then go around to those
particular machines and enable PXE and walk away.....I've done this type
of rule based participation multicast with brand new machines.....but
based on the answer above....if I can't make a multicast session and
base participation on hardware rules for machines that are already
imported, how do I go about making this process as unattended as do you guys handle such things and any other advice is
greatly appreciated.