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    Enabling IGMP on an Interface

    You must start IGMP on each interface that you want to use the protocol. You can configure IGMP and either PIM or DVMRP on the same interface. If you configure only IGMP on an interface, IGMP owns that interface. If you configure IGMP and either PIM or DVMRP on an interface, PIM or DVMRP owns the interface.

    By enabling IGMP, the router processes incoming multicast packets and creates an entry in the multicast routing table. If neither PIM nor DVMRP own the interface (for example, when only IGMP is configured), then the packets are locally routed to other interfaces on the router. PIM or DVMRP must be configured on the interface for packets to be sent to other routers.

    For networks that use only IGMPv1, you can configure an interface to operate in IGMPv1 mode. However, IGMPv2 and IGMPv3 interfaces support IGMPv1 hosts. In an IGMPv1 network, you must configure one interface to act as a querier. In an IGMPv2 or IGMPv3 network, the querier is the router with the lowest IP address.

    To start IGMP, complete the following steps:

    1. Enable IGMP on the interface (IGMPv2 is the default version).
      host1:boston(config-if)#ip igmp
    2. (IGMPv1 or IGMPv3) Specify the IGMP version for the interface.
      host1:boston(config-if)#ip igmp version 1
    3. (IGMPv1 only) Specify that the interface act as the querier for the network.
      host1:boston(config-if)#ip igmp querier

    Published: 2014-08-19