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IGMP snooping overview 2
connection to a PIM-enabled port, one of the devices must be configured as a querier. If multiple
devices are configured as queriers, after these devices exchange queries, then all except the
winner stop sending queries. The device with the lowest address becomes the querier. Although the
system will work when multiple devices are configured as queriers, Brocade recommends that only
one device (preferably the one with the traffic source) is configured as a querier.
The non-queriers always forward multicast data traffic and IGMP messages to router ports which
receive IGMP queries or PIM hellos. Brocade recommends that you configure the device with the
data traffic source (server) as a querier. If a server is attached to a non-querier, the non-querier
always forwards traffic to the querier regardless of whether there are any clients on the querier.
NOTE
In a topology of one or more connecting devices, at least one device must be running PIM configured
as active. Otherwise, none of the devices can send out queries, and traffic cannot be forwarded to
clients.
VLAN-specific configuration
IGMP snooping can be enabled on some VLANs or on all VLANs. Each VLAN can be independently
configured to be a querier or non-querier and can be configured for IGMP V2 or IGMP V3. In
general, the ip multicast commands apply globally to all VLANs except those configured with
VLAN-specific multicast commands. The VLAN-specific multicast commands supersede the global
ip multicast commands.
IGMP snooping can be configured for IGMP V2 or IGMP V3 on individual ports of a VLAN. An
interface or router sends the queries and reports that include its IGMP version specified on it. The
version configuration only applies to sending queries. The snooping device recognizes and
processes IGMP V2 and IGMP V3 packets regardless of the version configuration.
To avoid version deadlock, an interface retains its version configuration even when it receives a
report with a lower version.
Tracking and fast leave
Brocade devices support fast leave for IGMP V2, and tracking and fast leave for IGMP V3. Fast
leave stops the traffic immediately when the port receives a leave message. Tracking traces all
IGMP V3 clients. Refer to “Enabling IGMP V3 membership tracking and fast leave for the VLAN” on
page 39 and “Enabling fast leave for IGMP V2” on page 40.
Support for IGMP snooping and Layer 3 multicast routing
together on the same device
The Brocade device supports global Layer 2 IP multicast traffic reduction (IGMP snoopoing) and
Layer 3 multicast routing (PIM-Sparse or PIM-Dense) together on the same device in the full Layer 3
software image, as long as the Layer 2 feature configuration is at the VLAN level.
FastIron Ethernet Switch IP Multicast Configuration Guide 29
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