Configuration Guide User guide

1614 FastIron Configuration Guide
53-1002494-02
MLD Snooping Overview
• 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 “MLD snooping-enabled queriers and non-queriers” on
page 1614.
• 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
mld-snooping.. apply to all VLANs except those with a local mld-snooping.. 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.
Since Brocade does not support MRD, this can lead to stream loss when non-Querier router
ports age out on the Querier after the initial Query election. To avoid such stream loss,
configure a static router port on the querier on each interface that connects to a non-querier
snooping device.
MLD snooping-enabled queriers and non-queriers
An MLD snooping-enabled device can be configured as a querier (active) or non-querier (passive).
An MLD querier sends queries; a non-querier listens for MLD queries and forwards them to the
entire VLAN. When multiple MLD snooping devices are connected together, and there is no
connection to an IPv6 PIM-enabled port, one of the devices should be configured as a querier. If
multiple devices are configured as queriers, after multiple devices exchange queries, then all
devices except the winner (the device with the lowest address) stop sending queries. Although the
system works when multiple devices are configured as queriers, Brocade recommends that only
one device, preferably the one with the traffic source, is configured as the querier.
VLANs can also be independently configured as queriers or non-queriers. If a VLAN has a
connection to an IPv6 PIM-enabled port on another router, the VLAN should be configured as a
non-querier.