SMC Networks 6924MT, Management Manual

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Connecting VLAN Groups
The switch supports intra-VLAN communication using wire-speed
switching. However, if you have devices in separate VLANs that must
communicate, and it is not practical to include these devices in a common
VLAN, then the VLANs can be connected via a
Layer 3 switch (such as the SMC6724L3) or a router.
Multicast Filtering
Multicasting sends data to a group of nodes instead of a single destination.
The simplest way to implement multicasting is to broadcast data to all
nodes on the network. However, such an approach wastes a lot of
bandwidth if the target group is small compared to overall the broadcast
domain.
Since applications such as video conferencing and data sharing are more
widely used today, efficient multicasting has become vital. A common
approach is to use a group registration protocol that lets nodes join or
leave multicast groups. A switch or router can then easily determine which
ports contain group members and send data out to those ports only. This
procedure is called multicast filtering.
The purpose of multicast filtering is to optimize a switched network’s
performance, so multicast packets will only be forwarded to those ports
containing multicast group hosts or multicast routers/switches instead of
flooding to all ports in the subnet (VLAN). The TigerStack 100 supports
multicast filtering by passively monitoring IGMP Query and Report
messages.
IGMP Snooping
A Layer 2 switch can passively snoop on IGMP Query and Report packets
transferred between IP Multicast Routers/Switches and IP Multicast host
groups to learn the IP Multicast group members. It simply monitors the
IGMP packets passing through it, picks out the group registration