Thanks for the reponse Laz, I understand the difference between SDT & SPT but here’s where I get confused:
Even when running PIM dense mode with no RP, when I issue ‘show ip mroute’ I will see (1.1.1.1, 239.1.1.1) AND I will also see (,239.1.1.1). The (,239.1.1.1) will be for a device that has registered via IGMP to receive that multicast group. In this instance it doesnt have any link to sparse mode and RP as it is an IGMP join message.
So when is it used by IGMP join and then PIM Sparse mode as SDT? I’m confused by the notation (*,239.1.1.1) and its meaning when used by PIM Sparse RP and IGMP join.
I understand that for PIM Sparse RP the format is a wildcard for sources, but it is confusing that it is also used for IGMP join.