R3303-HP HSR6800 Routers IP Multicast Configuration Guide

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Figure 13 Network diagram
As shown in Figure 13, Router B operates as an IGMP snooping proxy. As a host from the perspective of
the querier Router A, Router B 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 messa
g
e Actions
General query
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.
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 of all router ports if the forwarding entry for the group still
contains a member port.
Report
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.
Leave
In response to an IGMP leave message for a multicast group, the proxy sends a
group-specific query out of the receiving port. After making sure that no member port is
contained in the forwarding entry for the multicast group, the proxy sends a leave
message to the group out of all router ports.
Host A
Receiver
Host B
Host C
Receiver
IGMP Querier
Router A
Proxy & Querier
Router B
Query from Router A
Report from Switch A
Query from Switch A
Report from Host
IP network