Netgear FS728TS - ProSAFE 24 Port 10/100 Stackable Smart Switch with 4 Gigabit Ports インストールガイド

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FS700TS Smart Switch Software Administration Manual
Configuring Switching Settings
4-29
v1.0, September 2007
Multicast
Multicast forwarding allows a single packet to be forwarded to multiple destinations. L2 Multicast 
service is based on L2 switch receiving a single packet addressed to a specific Multicast address. 
Multicast forwarding creates copies of the packet, and transmits the packets to the relevant ports. 
Registered Multicast traffic – If traffic addressed to a registered Multicast group is seen it is 
handled by an entry in the Multicast Filtering Database and forwarded only to the registered 
ports.
Unregistered Multicast traffic – If traffic addressed to an unregistered Multicast group is 
seen it is handled by a special entry in the Multicast Filtering Database. The default setting of 
this is to flood all such traffic (traffic in unregistered Multicast groups).
Layer 2 switching forwards Multicast packets to all relevant VLAN ports by default, treating the 
packet as a Multicast transmission. Multicast traffic forwarding is functional. However, irrelevant 
ports also receive the Multicast, causing increased network traffic. Multicast forwarding filters 
enable forwarding of Layer 2 packets to port subsets, defined in the Multicast filter database.
The device supports forwarding L2 Multicast Packets. Multicast forwarding is enabled by default, 
and not configurable by user. 
The Multicast menu contains the following options: 
Basic
The Multicast Basic menu contains the following options:
IGMP Snooping Configuration
When IGMP snooping is enabled, all IGMP packets are forwarded to the CPU. The CPU analyzes 
the incoming packets and determines which ports want to join which Multicast groups, which 
ports have Multicast routers generating IGMP queries, and what routing protocols are forwarding 
packets and Multicast traffic. Ports requesting to join a specific Multicast group issues an IGMP 
report specifying that Multicast group. This results in the creation of the Multicast filtering 
database.