D-Link DES-3250TG User Manual page 70

DES-3250TG Layer 2 Fast Ethernet Switch User's Guide
members on the network. IGMP is used to determine whether
the router should forward multicast packets it receives to the
subnetworks it is attached to or not. A multicast router that
has received a multicast packet will check to determine if there
is at least one member of a multicast group that has requested
to receive multicast packets from this source. If there is one
member, the packet is forwarded. If there are no members, the
packet is dropped.
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