H3C Technologies H3C S7500E Series Switches - Manual (Page 114)

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z If G is in the SSM group range but no IGMP SSM mappings corresponding to the multicast
group G have been configured on Router A, Router A cannot provide SSM service and
drops the message.
z 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.
z The IGMP SSM mapping feature does not process IGMPv3 reports.
z For more information about the SSM group range, refer to PIM Configuration in the IP
Multicast Configuration Guide.
IGMP Proxying
In some simple tree-shaped topologies, it is not necessary to configure complex multicast
routing protocols, such as PIM, on the boundary devices. Instead, you can configure IGMP
proxying on these devices. With IGMP proxying configured, the device serves as a proxy for the
downstream hosts to send IGMP messages, maintain group memberships, and implement
multicast forwarding based on the memberships. In this case, each boundary device is a host
but no longer a PIM neighbor to the upstream device.
Figure 5-4 Network diagram for IGMP proxying
Query from Router A
Report from Router B
Ethernet
Router interface
Host interface
Proxy & Querier
Router B
Querier
Router A
Host B
Receiver
Host A
Receiver
Host C
Query from Router B
Report from Host
PIM domain
As shown in Figure 5-4 , two types of interfaces are defined on an IGMP proxy device:
z Upstream interface: Also referred to as the proxy interface. A proxy interface is an interface
on which IGMP proxying is configured. It is in the direction toward the root of the multicast