Digisol DG-FS4526E, Management Manual

Page: 519 / 1162

C
HAPTER
18 | Multicast Filtering
Layer 2 IGMP (Snooping and Query)
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also request that service be forwarded from any source except for those
specified. In this case, traffic is filtered from sources in the Exclude list,
and forwarded from all other available sources.
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OTE
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When the switch is configured to use IGMPv3 snooping, the
snooping version may be downgraded to version 2 or version 1, depending
on the version of the IGMP query packets detected on each VLAN.
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IGMP snooping will not function unless a multicast router port is
enabled on the switch. This can accomplished in one of two ways. A static
router port can be manually configured (see "Specifying Static Interfaces
for a Multicast Router" on page 524 ). Using this method, the router port is
never timed out, and will continue to function until explicitly removed. The
other method relies on the switch to dynamically create multicast routing
ports whenever multicast routing protocol packets or IGMP query packets
are detected on a port.
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A maximum of up to 255 multicast entries can be maintained for
IGMP snooping. Once the table is full, no new entries are learned. Any
subsequent multicast traffic not found in the table is dropped if
unregistered-flooding is disabled (default behavior) and no router port is
configured in the attached VLAN, or flooded throughout the VLAN if
unregistered-flooding is enabled (see "Configuring IGMP Snooping and
Query Parameters" on page 520 ).
Static IGMP Router Interface – If IGMP snooping cannot locate the IGMP
querier, you can manually designate a known IGMP querier (i.e., a
multicast router/switch) connected over the network to an interface on
your switch ( page 524 ). This interface will then join all the current
multicast groups supported by the attached router/switch to ensure that
multicast traffic is passed to all appropriate interfaces within the switch.
Static IGMP Host Interface – For multicast applications that you need to
control more carefully, you can manually assign a multicast service to
specific interfaces on the switch ( page 525 ).
IGMP Snooping with Proxy Reporting – The switch supports last leave, and
query suppression (as defined in DSL Forum TR-101, April 2006):
When proxy reporting is disabled, all IGMP reports received by the
switch are forwarded natively to the upstream multicast routers.
Last Leave: Intercepts, absorbs and summarizes IGMP leaves coming
from IGMP hosts. IGMP leaves are relayed upstream only when
necessary, that is, when the last user leaves a multicast group.
Query Suppression: Intercepts and processes IGMP queries in such a
way that IGMP specific queries are never sent to client ports.
The only deviation from TR-101 is that the marking of IGMP traffic initiated
by the switch with priority bits as defined in R-250 is not supported.