Westermo PMI-110-F2G, User Manual

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4.9 Multicast Filtering
For multicast filtering, PMI Switch uses IGMP Snooping technology. IGMP
(Internet Group Management Protocol) is an Internet Protocol that provides a
way for internet device to report its multicast group membership to adjacent
routers. Multicasting allows one computer on the internet to send data to a
multitude of other computers that have identified themselves as being interested
in receiving the originating computers data.
Multicasting is useful for such applications as updating the address books of
mobile computer users in the field, sending out newsletters to a distribution list,
and broadcasting streaming media to an audience that has tuned into the event
by setting up multicast group membership.
In effect, IGMP Snooping manages multicast traffic by making use of switches,
routers, and hosts that support IGMP. Enabling IGMP Snooping allows the ports
to detect IGMP queries, report packets, and manage multicast traffic through the
switch. IGMP has three fundamental types of messages, as shown below:
Message Description
Query A message sent from the querier (an IGMP router or a switch)
which asks for a response from each host that belongs to the
multicast group.
Report A message sent by a host to the querier to indicate that the host
wants to be or is a member of a given group indicated in the
report message.
Leave Group A message sent by a host to the querier to indicate that the host
has quit as a member of a specific multicast group.
You can enable IGMP Snooping and IGMP Query functions here. You will see the
information of the IGMP Snooping function in this section, including different
multicast groups’ VID and member ports, and IP multicast addresses that range