H3C Technologies H3C S7500E Series Switches - Manual (Page 113)

5-6
added to the list; if the change was to an Exclude source list, these are the addresses that
were deleted from the list.
z BLOCK: indicates that the Source Address fields in this Group Record contain a list of the
sources that the system no longer wishes to hear from, for packets sent to the specified
multicast address. If the change was to an Include source list, these are the addresses that
were deleted from the list; if the change was to an Exclude source list, these are the
addresses that were added to the list.
IGMP SSM Mapping
The IGMP SSM mapping feature allows you to configure static IGMP SSM mappings on the last
hop router to provide SSM support for receiver hosts running IGMPv1 or IGMPv2. The SSM
model assumes that the last hop router is aware of the desired multicast sources when
receivers join multicast groups.
z When a host running IGMPv3 joins a multicast group, it can explicitly specify one or more
multicast sources in its IGMPv3 report.
z A host running IGMPv1 or IGMPv2, however, cannot specify multicast source addresses in
its report. In this case, you need to configure the IGMP SSM mapping feature to translate
the (*, G) information in the IGMPv1 or IGMPv2 report into (G, INCLUDE, (S1, S2...))
information.
Figure 5-3 Network diagram for IGMP SSM mapping
SSM
IGMPv1 report
IGMPv2 report
IGMPv3 report
Router A
Querier
Host A (IGMPv1) Host B (IGMPv2) Host C (IGMPv3)
Receiver Receiver Receiver
As shown in Figure 5-3 , on an SSM network, Host A, Host B and Host C are running IGMPv1,
IGMPv2 and IGMPv3 respectively. To provide SSM service for all the hosts while it is infeasible
to run IGMPv3 on Host A and Host B, you need to configure the IGMP SSM mapping feature on
Router A.
With the IGMP SSM mapping feature configured, when Router A receives an IGMPv1 or
IGMPv2 report, it checks the multicast group address G carried in the message:
z If G is not in the SSM group range, Router A cannot provide the SSM service but the ASM
service.