NBX 100/3com VoIP phones over a p2p T1 w/a 2500 and 3600.

We have a point-to-point T1 connecting our corporate office location
to our retail store location. Our retail store has housed our NBX 100
for a while, and hasn't really had any probs.

We're using a 2500 at the corporate office, and a 3600 at the store.
We've attained IP connectivity between the two sites, and basic phone
functionality works ok. However, I've come to understand some
functions (ie, real-time clock updating and conference calling)
require multicasting to be enabled.

I'm *very* green both to this phone system as well as IOS. From what
I understand, nobody did anything special as far as multicasting goes
during the original implementation at the store, so I don't know how
much management NBX NetSet does on its own...but could you kind folk
help to steer me in the right direction? How much is this going to
take on my part in IOS to get working? (One friend suggested I only
need a 224.0.0.0 route between the two sites, but he's not sure on how
exactly to implement it, and I've played around to no avail). I only
know the very base of basics when it comes to multicasting and have
never worked with any mcasting apps, and like I said, my IOS
experience is very limited as well...so this could be a rough one.
But TIA to any assistance offered.

PJ