3Com S7902E, Руководство по настройке

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1-6
IGMP Snooping Proxying
You can configure the IGMP snooping proxying function on an edge device, which then can represent
its attached hosts to send membership reports and leave messages, thus reducing the number of IGMP
reports and leave messages sent to its upstream device. The device configured with IGMP snooping
proxying is called an IGMP snooping proxy. It is a host from the perspective of its upstream device.
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 the IGMP report
suppression mechanism for hosts, refer to IGMP Configuration in the IP Multicast volume .
Figure 1-3 Network diagram for IGMP snooping proxying
As shown in Figure 1-3 , Switch A works as an IGMP Snooping proxy. It represents its attached hosts to
send membership reports and leave messages to Router A.
Table 1-2 describes how an IGMP snooping proxy processes IGMP messages.
Table 1-2 IGMP message processing on an IGMP snooping proxy
IGMP message Actions
General query
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.
Group-specific
query
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.