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Forum Replies

  1. Hi Rene,thanks for the explanation

    This behavior is the same for sparse mode as well?

  2. Hi Mungi,

    In this example, R4 is a host device where we used IGMP join to request multicast traffic on the interface.

    The PIM assert mechanism is only triggered when there are two routers on the same multi-access segment. When you connect R4 to R2 and R3 directly, you will be using two different segments so we don’t have to use PIM assert.

    Whether R4 will receive multicast traffic will depend if you configured IGMP join. If you do this on both interfaces then it will receive multicast traffic on both interfaces.

    Rene

  3. Hi Jose,

    It’s very likely to see PIM assert in dense mode since we flood everything. It’s unlikely to encounter in sparse mode but it does exist. Let me give you an example. Take a look at the “pim-sparse-assert.png” image in the attachment for the topology.

    On top, we have the RP, connected to R1/R2. At the bottom we have R3/R4 with a receiver each.

    R1/R2/R3/R4 are connected to the same multi-access segment through the switch.

    • R3 uses R1 to get to the RP.
    • R4 uses R1 to get to the RP.

    Let’s say our receivers both join group 239.1.1.1. This is what happens:

    R3

    ... Continue reading in our forum

  4. Hi Rene,
    Sometimes PIM DR and PIM forwrder do the same role? I meant when you told don’t confuse this 2 features I’am confuse.

  5. Hi Djan,

    The DR has two roles:

    - Send PIM register packets from source to RP.
    - Forward PIM join/prune packets towards the RP.

    The forwarder does something else. It ensures that downstream multicast traffic (from source to receiver) is only forwarded on a multi-access segment by one router, not two (otherwise we get duplicate packets).

    Rene

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