Configuration Guide User guide

FastIron Configuration Guide 1613
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MLD Snooping Overview
For two multicast traffic streams, Source_1 and Group1 (S1,G1) and Source_2 and Group2
(S2,G2), with the same or different source addresses, if the lowest 32 bits of the 128-bit IPv6
group address are the same, they would map to the same destination MAC. Because the FESX and
FSX support MAC-based forwarding for MLD snooping, the final multicast MAC address entry would
be a superset of all the IPv6 groups mapped to it. For example, consider the following three IPv6
multicast streams sent from port 5 of a Brocade device:
• (S1,G1) = (2060::5, ff1e::12), client port 1, port 2
• (S2,G2) = (2060::6, ff1e::12), client port 2, port 3
• (S3,G1) = (2060::7, ff1e::12), client port 4
Because the lowest 32 bits of the group address for G1 and G2 are the same, all three streams
would use 0x33-33-00-00-00-12 as the destination MAC address. MLD snooping would build a
MAC entry with the MAC address 0x33-33-00-00-00-12 on egress ports 1, 2, 3, and 4. As a result,
all three streams would be sent to ports 1, 2, 3, and 4. Note that the above example assumes the
following:
• The Brocade device is running MLD snooping on VLAN 10 and all three streams are in VLAN 10
• There are clients on port 1 and port 2 for (S1,G1)
• There are clients on port 2 and port 3 for (S2,G2)
• There are clients on port 4 for (S3,G1)
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 the example given
in the preceding section (“How MLD snooping uses MAC addresses to forward multicast
packets” on page 1612), (S1,G1) and (S3,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.
• Up to 4K collective entries for IGMP Snooping, MLD snooping, and Multi-port Static MAC
Addresses are supported.
• 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.