Layer 2 Igmp (Snooping And Query) - SMC Networks SMC TigerStack III SMC6824M Management Manual

M F
ULTICAST ILTERING
multicast host registration protocol that allows any host to inform its local
router that it wants to receive transmissions addressed to a specific
multicast group.
A router, or multicast-enabled switch, can periodically ask their hosts if
they want to receive multicast traffic. If there is more than one router/
switch on the LAN performing IP multicasting, one of these devices is
elected "querier" and assumes the role of querying the LAN for group
members. It then propagates the service requests on to any adjacent
multicast switch/router to ensure that it will continue to receive the
multicast service.
Based on the group membership information learned from IGMP, a
router/switch can determine which (if any) multicast traffic needs to be
forwarded to each of its ports. At Layer 3, multicast routers use this
information, along with a multicast routing protocol such as DVMRP or
PIM, to support IP multicasting across the Internet.
Note that IGMP neither alters nor routes IP multicast packets. A multicast
routing protocol must be used to deliver IP multicast packets across
different subnetworks. Therefore, when DVMRP or PIM routing is
enabled for a subnet on this switch, you also need to enable IGMP.

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 3-222) to monitor IGMP service requests passing between
multicast clients and servers, and dynamically configure the switch ports
which need to forward multicast traffic.
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 3-225). 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.
3-221