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In PIM Dense Mode, why does an Assert loser send a Prune message to the winner? What is the actual motivation for this?

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I found a post that answers my question. For anyone that might be interested:

https://community.cisco.com/t5/routing/pim-dense-mode-duplicate-traffic/m-p/4788788

Edit: So the answer to my question is: simply to inform the winner to stop sending traffic because it doesn't need it. Now, there are more scenarios that may appear:

  • Scenario 1: there are only the two routers on the segment: In this case the winner receives the PIM Prune message and it stops sending the traffic.
  • Scenario 2: there is a third router (downstream) on the segment: In which case, both the winner and the third router receive the PIM Prune message, and the third router responds to it by sending a PIM Join to override the PIM Prune sent by the loser.
  • Scenario 3: there is an IGMP receiver on the segment: in which case the winner won't stop forwarding traffic, I assume that because of the IGMP active client.
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    Please add details to your answer so this post remains useful even if the linked page changes or disappears.
    – Teun Vink
    May 7, 2023 at 13:01

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