HP A8800 Configuration Manual page 30

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
Figure 13 Network diagram
As shown in Figure 13, Device A works as an IGMP snooping proxy. As a host from the perspective of
the querier Router A, Device A represents its attached hosts to send membership reports and leave
messages to Router A.
Table 6 describes how an IGMP snooping proxy processes IGMP messages.
Table 6 IGMP message processing on an IGMP snooping proxy
IGMP message
General query
Group-specific query
Report
Actions
When receiving an IGMP general query, the proxy forwards it to all ports except
the port that receive the query. In addition, the proxy generates a report
according to the group membership that it maintains and sends the report out of
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 of all router ports if the forwarding entry
for the group still contains a member port.
After receiving a report for a multicast group, the proxy looks up the multicast
forwarding table for the forwarding entry for the multicast group.
•
If a forwarding entry matches the multicast group and contains the receiving
port as a dynamic member port, the proxy restarts the aging timer for the
port.
•
If a forwarding entry matches the multicast group but does not contain the
receiving port, the proxy adds the port to the forwarding entry as a dynamic
member port and starts an aging timer for the port.
•
If no forwarding entry matches the multicast group, the proxy creates a
forwarding entry for the multicast group, adds the receiving port to the
forwarding entry as a dynamic member port, and starts an aging timer for the
port.
18
"Configuring IGMP."