96
{
BLOCK
—The Source Address fields contain a list of the sources from which the receiver no
longer wants to obtain data. If the current filtering mode is Include, these sources are
deleted from the multicast source list. If the current filtering mode is Exclude, these sources
are added to the multicast source list.
IGMP SSM mapping
The IGMP SSM mapping feature enables you to configure static IGMP SSM mappings on the
last-hop router to provide SSM support for receiver hosts that are running IGMPv1 or IGMPv2. The
SSM model assumes that the last-hop router has identified the desired multicast sources when
receivers join multicast groups.
•
When a host that is running IGMPv3 joins a multicast group, it can explicitly specify one or more
multicast sources in its IGMPv3 report.
•
A host that is running IGMPv1 or IGMPv2, however, cannot specify multicast source addresses
in its report. In this case, you must configure the IGMP SSM mapping feature to translate the (*,
G) information in the IGMPv1 or IGMPv2 report into (G, INCLUDE, (S1, S2...)) information.
Figure 35 Network diagram
As shown in
, on an SSM network, Host A, Host B and Host C run IGMPv1, IGMPv2 and
IGMPv3 respectively. To provide SSM service for all hosts if IGMPv3 is not available on Host A and
Host B, you must 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 examines the multicast group address G carried in the message and does the following:
•
If G is not in the SSM group range, Router A cannot provide the SSM service but can provide
the ASM service.
•
If G is in the SSM group range but no IGMP SSM mappings that correspond to the multicast
group G have been configured on Router A, Router A cannot provide SSM service and drops
the message.
•
If G is in the SSM group range and the IGMP SSM mappings have been configured on Router A
for multicast group G, Router A translates the (*, G) information in the IGMP report into (G,
INCLUDE, (S1, S2...)) information based on the configured IGMP SSM mappings and provides
SSM service accordingly.
NOTE:
The IGMP SSM mapping feature does not process IGMPv3 reports.
