(*,G) entries upstream of the RP in sparse mode

Hi
I have a short question.
we have a sparse mode scenario with static RP - R3 with this topology
from antonio soares lab:
http://ccie18473.net/dynamips/dynamips.htm#pim-sm
Topology is : Source-R1-R2-R3-R4-R5-Receiver
Why do we have on R1, and R2 (*,G ) entries when sending traffic from
the source ? I know that is normal to have it dowstream of the RP but
i don't understand whey we have it upstream of the RP ? Is it for
dense mode fallback ?

R1#sh ip mroute 224.1.1.1
(*, 224.1.1.1), 00:00:26/stopped, RP 3.3.3.3, flags: SPF
  Incoming interface: Serial1/1, RPF nbr 12.12.12.2
  Outgoing interface list: Null
(10.10.10.1, 224.1.1.1), 00:00:26/00:03:28, flags: FT
  Incoming interface: FastEthernet0/0, RPF nbr 0.0.0.0
  Outgoing interface list:
    Serial1/1, Forward/Sparse, 00:00:26/00:03:04

br
Ovidiu

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Received on Sat Aug 21 2010 - 13:46:18 ART