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  1. Rene,

    Great lesson, however I have a question about for the host don’t we need ip pim sparse-mode? I can see on the router we have ip pim sparse-mode.

    Please clarify.




  2. great post.

    with respect to below 2 statements: what is the diff between multicast-routing and PIM command ? both seems to be doing same thing - process the IGMP traffic.

    1.First we enabled multicast routing globally, this is required for the router to process IGMP traffic.
    2.We enabled PIM on the interface. PIM is used for multicast routing between routers and is also required for the router to process IGMP traffic.

    a. from where .40 address came ? does router generates it randomly ?
    b. group address who decides and gives this IP in real time environment ?

  3. IGMP version 1 only had two messages: the membership query and membership reply. There was no message that allowed a host to inform that he didn’t want to receive multicast traffic for a certain group anymore. It was possible that a router would forward packets to a certain multicast group with no listeners anymore…

    So with traffic, I meant the actual video/audio/application traffic for the multicast group that the listeners are interested in.

  4. Hi,

    R1#show ip igmp groups
    IGMP Connected Group Membership
    Group Address    Interface                Uptime    Expires   Last Reporter   Group Accounted        GigabitEthernet0/1       19:22:56  00:01:07

    Can you explain
    Why the host cannot see cant see here

  5. There are two options that come to mind:

    R1#show ip multicast                   
            Multicast Routing: enabled
            Multicast Multipath: disabled
            Multicast Route limit: No limit
            Multicast Triggered RPF check: enabled
            Multicast Fallback group mode: Sparse
            Multicast DVMRP Interoperability: disabled

    Or just check the running config:

    R1#show run | include multicast-routing
    ip multicast-routing

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