HP 6125G HP 6125G & 6125G/XG Blade Switches IP Multicast Configuration - Page 27

to Router A., IGMP message, Actions

Page 27 highlights

Figure 12 Network diagram IP network IGMP Querier Router A Proxy & Querier Switch A Query from Router A Report from Switch A Query from Switch A Report from Host Host A Receiver Host B Host C Receiver As shown in Figure 12, Switch A works as an IGMP snooping proxy. As a host from the perspective of 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 Report Leave 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 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. 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. 16

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16
Figure 12
Network diagram
As shown in
Figure 12
, Switch A works as an IGMP snooping proxy. As a host from the perspective of 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
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 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
Switch A
Query from Router A
Report from Switch A
Query from Switch A
Report from Host
IP network