User manual

C HAPTER 17 | Multicast Filtering
Layer 2 IGMP (Snooping and Query)
– 276 –
ES-2000 Series
containing multicast group hosts or multicast routers/switches, instead of
flooding traffic to all ports in the subnet (VLAN).
LAYER 2 IGMP (SNOOPING AND QUERY)
IGMP Snooping and Query – If multicast routing is not supported on other
switches in your network, you can use IGMP Snooping and IGMP Query
(page 277) to monitor IGMP service requests passing between multicast
clients and servers, and dynamically configure the switch ports which need
to forward multicast traffic. IGMP Snooping conserves bandwidth on
network segments where no node has expressed interest in receiving a
specific multicast service. For switches that do not support multicast
routing, or where multicast routing is already enabled on other switches in
the local network segment, IGMP Snooping is the only service required to
support multicast filtering.
N OTE : When the switch is configured to use IGMPv2 snooping, the
snooping version may be downgraded to version 1, depending on the
version of the IGMP query packets detected on each VLAN.
N OTE : 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 280). 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.
N OTE : 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 277).
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 280). 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 282).