
Explanation:
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PIM-DM supports only source trees - that is, (S,G) entries-and cannot be used to build a shared distribution tree.
Reference:https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipmulti_pim/configuration/xe-16-5/imc-pim-xe-16 PIM dense mode (PIM-DM) uses apush modelto flood multicast traffic to every corner of the network. This push model is a brute-force method of delivering data to the receivers. This method would be efficient in certain deployments in which there are active receivers on every subnet in the network. PIM-DM initially floods multicast traffic throughout the network. Routers that have no downstream neighborsprune the unwanted traffic. This process repeats every 3 minutes.
A rendezvous point (RP) is required only in networks running Protocol Independent Multicast sparse mode (PIM-SM).
In PIM dense mode (PIM-DM), multicast traffic is initially flooded to all segments of the network. Routers that have no downstream neighbors or directly connected receivers prune back the unwanted traffic.