PLANET SGSD-1022 - Manual (Page 212)

User’s Manual of SGSD-1022 / SGSD-1022P
SGSW-2840 / SGSW-2840P
Configuring IGMP Snooping and Query Parameters
4.9.1.1 IGMP Configuration
You can configure the Managed Switch to forward multicast traffic intelligently. Based on the IGMP query and report messages,
the Managed Switch forwards traffic only to the ports that request multicast traffic. This prevents the Managed Switch from
broadcasting the traffic to all ports and possibly disrupting network performance.
Command Usage
„ IGMP Snooping –
This Managed Switch can passively snoop on IGMP Query and Report packets transferred between IP multicast
routers/switches and IP multicast host groups to identify the IP multicast group members. It simply monitors the IGMP
packets passing through it, picks out the group registration information, and configures the multicast filters accordingly.
Unknown multicast traffic is flooded to all ports in the VLAN for several seconds when first
received. If a multicast router port exists on the VLAN, the traffic will be filtered by subjecting
it to IGMP snooping. If no router port exists on the VLAN or the multicast filtering table is
already full, the switch will continue flooding the traffic into the VLAN.
„ IGMP Querier –
A router, or multicast-enabled switch, can periodically ask their hosts if they want to receive multicast traffic. If there is more
than one router/switch on the LAN performing IP multicasting, one of these devices is elected “querier” and assumes the
role of querying the LAN for group members. It then propagates the service requests on to any upstream multicast
switch/router to ensure that it will continue to receive the multicast service.
Multicast routers use this information, along with a multicast routing protocol such as
DVMRP or PIM, to support IP multicasting across the Internet.
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