NETGEAR M4350-24F4V 24-Port 10G SFP+ Managed AV Network Switch - Manual (Page 307)

Internet Group Management
Protocol snooping
Internet Group Management Protocol (IGMP) snooping allows a switch to forward
multicast traffic intelligently. Multicast IP traffic is destined to a host group. Host groups
are identified by class D IP addresses, which range from 224.0.0.0 to 239.255.255.255.
Based on the IGMP query and report messages, the switch forwards traffic only to the
ports that request the multicast traffic. This prevents the switch from broadcasting the
traffic to all ports and possibly affecting network performance.
A traditional Ethernet network can be separated into different network segments to
prevent placing too many devices onto the same shared media. Bridges and switches
connect these segments. When a packet with a broadcast or multicast destination
address is received, the switch forwards a copy into each of the remaining network
segments in accordance with the IEEE MAC Bridge standard. Eventually, the packet is
made accessible to all nodes connected to the network.
This approach works well for broadcast packets that are intended to be seen or
processed by all connected nodes. In the case of multicast packets, however, this
approach could lead to less efficient use of network bandwidth, particularly when the
packet is intended for only a small number of nodes. Packets are flooded into network
segments where no node is receptive to the packet. While nodes rarely incur any
processing overhead to filter packets addressed to unrequested group addresses, they
cannot transmit new packets onto the shared media during the period that the multicast
packet is flooded. The problem of wasting bandwidth is even worse when the LAN
segment is not shared, for example in full-duplex links.
Allowing switches to snoop IGMP packets is a creative effort to solve this problem. The
switch uses the information in the IGMP packets as they are being forwarded throughout
the network to determine which segments receive packets directed to the group address.
Configure IGMP snooping automatically with
IGMP Plus mode
IGMP Plus mode lets you automatically configure IGMP snooping, which is used to build
forwarding lists for IPv4 multicast traffic.
You can also configure IGMP snooping manually (see Configure IGMP snooping manually
on page 309).
Main User Manual 307 Configure Switching Information
Fully Managed Switches M4350 Series Main User Manual