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IGMP Snooping
IGMP snooping requires the LAN switch to examine, or snoop, some
Layer 3 information in the IGMP packets sent between the hosts and the
router. When the switch hears the IGMP host report from a host for a
particular multicast group, the switch adds the host's port number to the
associated multicast table entry. When the switch hears the IGMP leave
group message from a host, it removes the host's port from the table
entry.
Multicast Forwarding
In multicast routing, the source is sending traffic to an arbitrary group of
hosts represented by a multicast group address. The multicast router
must determine which direction is upstream (toward the source) and
which direction (or directions) is downstream. If there are multiple down-
stream paths, the router replicates the packet and forwards the traffic
down the appropriate downstream paths - which is not necessarily all
paths.
The switch can support IP multicast if IGMP protocol is enabled. IGMP
snooping function and status is also provided. Each IP multicast address
is associated one Vlan ID and its member ports. The information is avail-
able from management interfaces.
1.5.3 MAC Address Filtering Function
MAC address filtering allows the switch to drop unwanted traffic. In-
coming traffic is filtered based on the destination MAC addresses (DAs).
The unwanted destination addresses are called filter MAC addresses.
The switch provides management function that allows LAN administra-
tor to maintain the filter MAC address table.