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8‐Port Gigabit Web‐Smart Switch
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P a g e
3.3
MultiCast
3.3.1
IGMP Snooping
The Internet Group Management Protocol (IGMP) lets hosts and routers share information about
multicast group memberships. IGMP snooping is a switch feature that monitors the exchange of IGMP
messages and copies them to the CPU for future processing. The overall purpose of IGMP Snooping is to
limit the forwarding of multicast frames to only ports that are a member of the multicast group.
About the Internet Group Management Protocol (IGMP) Snooping
Computers and network devices that want to receive multicast transmissions need to inform nearby
routers that they will become members of a multicast group. The Internet Group Management Protocol
(IGMP) is used to communicate this information. IGMP is also used to periodically check the multicast
group for members that are no longer active. In the case where there is more than one multicast router
on a sub network, one router is elected as the ‘queried’. This router then keeps track of the membership
of the multicast groups that have active members. The information received from IGMP is then used to
determine if multicast packets should be forwarded to a given sub network or not. The router can check,
using IGMP, to see if there is at least one member of a multicast group on a given subnet work. If there are
no members on a sub network, packets will not be forwarded to that sub network.
Multicast Service
You can enable or disable IGMP Snooping on this screen.