User Guide
is unable to install resources for a specific matching address due to hashing collision. The hardware
hashes addresses into available entries, with some addresses hashed into the same entry. If the
collision number in an entry is more than the hardware chain length, the resource cannot be installed.
MLD snooping configuration notes and feature limitations
• Servers (traffic sources) are not required to send Multicast Listening Discovery (MLD)
memberships.
• The default MLD version is V1, where the source address is not sensitive. In this version, (S1,G1)
and (S2,G1) would be considered the same group as (*,G1).
• If MLDv2 is configured on any port of a VLAN, you can check the source information, but because
MLD snooping is MAC based, (S,G) switching is not feasible.
• Hardware resources are installed only when there is data traffic.
• You can configure the maximum number of groups and the multicast cache (mcache) number.
• The device supports static groups applying to specific ports. The device acts as a proxy to send
MLD reports for the static groups when receiving queries.
• A user can configure static router ports, forcing all multicast traffic to be sent to these ports.
• Brocade devices support fast leave for MLDv1, which stops traffic immediately to any port that
has received a leave message.
• Brocade devices support tracking and fast leave for MLDv2, which tracks all MLDv2 clients. If the
only client on a port leaves, traffic is stopped immediately.
• An MLD device can be configured as a querier (active) or non-querier (passive). Queriers send
queries. Non-queriers listen for queries and forward them to the entire VLAN.
• Every VLAN can be independently configured as a querier or a non-querier.
• A VLAN that has a connection to an IPv6 PIM-enabled port on another router should be
configured as a non-querier. When multiple snooping devices connect together and there is no
connection to IPv6 PIM ports, only one device should be configured as the querier. If multiple
devices are configured as active, only one will continue to send queries after the devices have
exchanged queries. Refer to the MLD snooping-enabled queriers and non-queriers section.
• An MLD device can be configured to rate-limit the forwarding of MLDv1 membership reports to
queriers.
• Because an IPv6 link-local address as the source address when sending queries, a global
address is not required.
• The MLD implementation allows snooping on some VLANs or on all VLANs. MLD can be enabled
or disabled independently for each VLAN. In addition, individual ports of a VLAN can be
configured as MLDv1 and MLDv2. In general, global configuration commands such as ipv6
multicast.. apply to all VLANs except those with a local multicast6.. configuration, which
supersedes the global configuration. Configuring the version on a port or a VLAN only affects the
device sent query version. The device always processes all versions of client reports regardless
of the version configured.
• MLD snooping requires hardware resources. If the device has insufficient resources, the data
stream without a resource is mirrored to the CPU in addition to being VLAN flooded, which can
cause high CPU usage. To avoid this situation, Brocade recommends that you avoid enabling
snooping globally unless necessary.
• To receive data traffic, MLD snooping requires clients to send membership reports. If a client does
not send reports, you must configure a static group to force traffic to client ports.
• Multicast Router Discovery (MRD) messages are useful for determining which nodes attached to
a switch have multicast routing enabled. This capability is useful in a Layer 2 bridge domain with
snooping switches. By utilizing MRD messages, Layer 2 switches can determine where to send
multicast source data and group membership messages. Multicast source data and group
membership reports must be received by all multicast routers on a segment. Using the group
membership protocol Query messages to discover multicast routers is insufficient due to query
suppression.
MLD snooping configuration notes and feature limitations
46 FastIron Ethernet Switch IP Multicast Configuration Guide
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