Brocade TurboIron 24X Series Configuration Guide - Manual (Page 802)

768 Brocade TurboIron 24X Series Configuration Guide
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IGMP snooping overview
• Filter-mode-change record. If the interface state changes from IS_IN to IS_EX, a TO_EX record
is included in the membership report. Likewise, if the interface state changes from IS_EX to
IS_IN, a TO_IN record appears in the membership report.
• An IGMP V2 leave report is equivalent to a TO_IN (empty) record in IGMP V3. This record means
that no traffic from this group will be received regardless of the source.
• An IGMP V2 group report is equivalent to an IS_EX (empty) record in IGMP V3. This record
means that all traffic from this group will be received regardless of source.
• Source-list-change record. If the interface wants to add or remove traffic sources from its
membership report, the report can contain an ALLOW record, which includes a list of new
sources from which the interface wishes to receive traffic. It can also contain a BLOCK record,
which lists the current traffic sources from which the interface wants to stop receiving traffic.
IGMP protocols provide a method for clients and a device to exchange messages, and let the device
build a database indicating which port wants what traffic. The protocols do not specify forwarding
methods. They require IGMP snooping or multicast protocols such as PIM to handle packet
forwarding. PIM can route multicast packets within and outside a VLAN, while IGMP snooping can
switch packets only within a VLAN.
If a VLAN is not IGMP snooping-enabled, it floods multicast data and control packets to the entire
VLAN in hardware. When snooping is enabled, IGMP packets are trapped to the CPU. Data packets
are mirrored to the CPU in addition to being VLAN flooded. The CPU then installs hardware
resources, so that subsequent data packets can be switched to desired ports in hardware without
going to the CPU. If there is no client report or port to queriers for a data stream, the hardware
resource drops it.
Devices, the hardware can either match the group address only (* G), or both the source and group
(S G) of the data stream. If any IGMPv3 is configured in any port of a VLAN, this VLAN uses (S G)
match; otherwise, it uses (* G). This is 32-bit IP address matching, not 23-bit multicast MAC
address 01-00-5e-xx-xx-xx matching.
Devices support up to 2K of IGMP groups, which are produced by client membership reports.
IGMP V1, V2, and V3 snooping support
Table 114 shows IGMP snooping version support.
Queriers and non-queriers
An IGMP snooping-enabled device can be configured as a querier (active) or non-querier (passive).
An IGMP querier sends queries; a non-querier listens for IGMP queries and forwards them to the
entire VLAN. VLANs can be independently configured to be queriers or non-queriers. If a VLAN has a
connection to a PIM-enabled port on another router, the VLAN should be configured as a
non-querier. When multiple IGMP snooping devices are connected together, and there is no
connection to a PIM-enabled port, one of the devices should be configured as a querier. If multiple
TABLE 114 IGMP snooping support
Software release IGMP version support Supported in software code...
TurboIron X Series series devices IGMP V1 snooping
IGMP V2 snooping
IGMP V3 snooping L2