As per my understanding, you will need to configure RP if you are running Sparse Mode PIM.
The below KB gives details about configuration:https://kb.juniper.net/InfoCenter/index?page=content&id=KB13329
The dense mode works best in networks where few or no prunes occur. I see you have a simple set-up. This could be your choice.
In such instances, the dense mode is actually more efficient than the sparse mode. PIM dense mode is less sophisticated than PIM sparse mode. PIM dense mode is useful for multicast LAN applications, the main environment for all dense mode protocols. PIM dense mode implements the same flood-and-prune mechanism that DVMRP and other dense mode routing protocols employ.
The main difference between DVMRP and PIM dense mode is that PIM dense mode introduces the concept of protocol independence. PIM dense mode can use the routing table populated by any underlying unicast routing protocol to perform reverse-path-forwarding (RPF) checks.
Unlike sparse mode, in which data is forwarded only to routing devices sending an explicit request, dense mode implements a flood-and-prune mechanism, similar to DVMRP. In PIM dense mode, there is no RP.
The below document will give you an overview and to the left side of the page, you can navigate to the configuration:https://www.juniper.net/documentation/en_US/junos/topics/concept/multicast-pim-overview.html
The below document has a detailed troubleshooting guide of Multicast w.r.t Juniper. If you run into issues or need information, this is the go-to page.https://kb.juniper.net/InfoCenter/index?page=content&id=KB21586&actp=METADATA
Hope this helps 🙂
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