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Cisco Catalyst Blade Switch 3130 for Dell Software Configuration Guide
OL-13270-01
Chapter23 Configuring IGMP Snooping and M VR Understanding IGMP Snooping
IGMP Versions
The switch supports IGMP Version 1, IGMP Version 2, and IGMP Version 3. These versions are
interoperable on the switch. For example, if IGMP snooping is ena ble d on an I GM Pv2 swi tch and the
switch receives an IGMPv3 report from a host, the switch can forward the IGMPv3 report to the
multicast router.
Note The switch supports IGMPv3 snooping based only on the destination multicast MAC address. It does not
support snooping based on the source MAC address or on proxy reports.
An IGMPv3 switch supports Basic IGMPv3 Snooping Support (BISS), which incl udes supp ort for t he
snooping features on IGMPv1 and IGMPv2 switches and for IG MPv 3 mem bersh ip r ep ort messa ge s.
BISS constrains the flooding of multicast traffic when your network includes IGMPv3 hosts. It
constrains traffic to approximately the same set of ports as the IGMP snooping feature on IGMPv2 or
IGMPv1 hosts.
Note IGMPv3 join and leave messages are not supported on switches running IGMP filtering or MVR.
An IGMPv3 switch can receive messages from and forward messages to a device running the So urce
Specific Multicast (SSM) feature. For more information about source-specific multicast with IGMPv3
and IGMP, see this URL:
http://www.cisco.com/en/US/products/sw/iosswrel/ps1834/products_feature_guide09186a008008048a.
html
Joining a Multicast Group
When a blade server connected to the switch wants to join an IP multicast group and it is an IGMP
Version 2 client, it sends an unsolicited IGMP join message, specifying the IP multicast group to join.
Alternatively, when the switch receives a general query from the router, it forwards the query to all ports
in the VLAN. IGMP Version 1 or Version 2 blade servers wanting to join the multicast group respond
by sending a join message to the switch. The switch CPU creates a multicast forwarding-table entry for
the group if it is not already present. The CPU also adds the interface where the join message was
received to the forwarding-table entry . Th e blade serv er a ssoci ated with that inter face re cei v es m ultica st
traffic for that multicast group. See Figure23-1.