IGMP SSM mapping

An IGMPv3 host can explicitly specify multicast sources in its IGMPv3 reports. From the reports, the IGMP device can obtain the multicast source addresses and directly provide the SSM service. However, an IGMPv1 or IGMPv2 host cannot specify multicast sources in its IGMPv1 or IGMPv2 reports.

The IGMP SSM mapping feature enables the IGMP device to provide SSM support for IGMPv1 or IGMPv2 hosts. The device translates (*, G) in IGMPv1 or IGMPv2 reports into (G, INCLUDE, (S1, S2...)) based on the configured IGMP SSM mappings.

Figure 36: IGMP SSM mapping

As shown in Figure 36, on an SSM network, Host A, Host B, and Host C run IGMPv1, IGMPv2, and IGMPv3, respectively. To provide the SSM service for Host A and Host B, you must configure the IGMP SSM mapping feature on Device A.

After IGMP SSM mappings are configured, Device A checks the multicast group address G in the received IGMPv1 or IGMPv2 report, and performs the following operations:


[NOTE: ]

NOTE:

The IGMP SSM mapping feature does not process IGMPv3 reports.


For more information about SSM group ranges, see "Configuring PIM."