Igmp Snooping Proxying - HP A5500 SI Switch Series Configuration Manual

If the port receives no IGMP report in response to the group-specific query before its aging timer
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expires, it indicates that no hosts attached to the port are still monitoring that group address. The
switch removes the port from the outgoing port list of the entry in the forwarding table for that
multicast group when the aging timer expires.

IGMP snooping proxying

The IGMP snooping proxying function on an edge device reduces the number of IGMP reports and
leave messages sent to its upstream device. The device configured with IGMP snooping proxying is
called "IGMP snooping proxy." It is a host from the perspective of its upstream device.
NOTE:
Even though an IGMP snooping proxy is a host from the perspective of its upstream device, the IGMP
membership report suppression mechanism for hosts does not take effect on it. For more information
about the IGMP report suppression mechanism for hosts, see the chapter "IGMP configuration."
Figure 13 Network diagram for IGMP snooping proxying
As shown in
the querier Router A, Switch A represents its attached hosts to send membership reports and leave
messages to Router A.
Table 6 IGMP message processing on an IGMP snooping proxy
IGMP message
General query
Group-specific query
Figure 13, Switch A works as an IGMP snooping proxy. As a host from the perspective of
Actions
When receiving an IGMP general query, the proxy forwards it to all
ports but the receiving port. In addition, the proxy generates a report
according to the group memberships it maintains and sends the report
out all router ports.
In response to the IGMP group-specific query for a certain multicast
group, the proxy sends the report to the group out all router ports if
the forwarding entry for the group still contains a member port.
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