Joining An Ipv6 Multicast Group - Cisco WS-SUP32-GE-3B - Supervisor Engine 32 Software Configuration Manual

Chapter 26 Configuring MLDv2 Snooping for IPv6 Multicast Traffic
Understanding How MLDv2 Snooping Works
Disabling explicit host tracking disables fast-leave processing and proxy reporting.
Note

Joining an IPv6 Multicast Group

Hosts join IPv6 multicast groups either by sending an unsolicited MLDv2 report or by sending an
MLDv2 report in response to a general query from an IPv6 multicast router (the switch forwards general
queries from IPv6 multicast routers to all ports in a VLAN). The switch snoops these reports.
In response to a snooped MLDv2 report, the switch creates an entry in its Layer 2 forwarding table for
the VLAN on which the report was received. When other hosts that are interested in this multicast traffic
send MLDv2 reports, the switch snoops their reports and adds them to the existing Layer 2 forwarding
table entry. The switch creates only one entry per VLAN in the Layer 2 forwarding table for each
multicast group for which it snoops an MLDv2 report.
MLDv2 snooping suppresses all but one of the host reports per multicast group and forwards this one
report to the IPv6 multicast router.
The switch forwards multicast traffic for the multicast group specified in the report to the interfaces
where reports were received (see Figure 26-1).
Layer 2 multicast groups learned through MLDv2 snooping are dynamic. However, you can statically
configure Layer 2 multicast groups using the mac-address-table static command. When you specify
group membership for a multicast group address statically, the static setting supersedes any MLDv2
snooping learning. Multicast group membership lists can consist of both static and MLDv2
snooping-learned settings.
Figure 26-1 Initial MLDv2 Listener Report
Router A
1
MLDv2 report
VLAN
PFC
CPU
0
Forwarding
table
2 3 4 5
Host 1 Host 2 Host 3 Host 4
Multicast router A sends an MLDv2 general query to the switch, which forwards the query to ports 2
through 5 (all members of the same VLAN). Host 1 wants to join an IPv6 multicast group and multicasts
an MLDv2 report to the group with the equivalent MAC destination address of 0x0100.5E01.0203.
Catalyst Supervisor Engine 32 PISA Cisco IOS Software Configuration Guide, Release 12.2ZY
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