User's Manual

User’s Manual of SGS-5240 Series Managed Switch
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◆Release Mode – Configures the interface for automatic or manual loopback release. (Default: Auto)
◆Release – Allows an interface to be manually released from discard mode. This is only available if the interface is configured
for manual release mode.
◆Action – Sets the response for loopback detection to block user traffic or shut down the interface. (Default: Block)
◆Shutdown Interval – The duration to shut down the interface. (Range: 60-86400 seconds; Default: 60 seconds)
If an interface is shut down due to a detected loopback, and the release mode is set to “Auto,” the selected interface will be
automatically enabled when the shutdown interval has expired. If an interface is shut down due to a detected loopback, and the
release mode is set to “Manual,” the interface can be re-enabled using the Release button.
4.2.11 IGMP Snooping
The Internet Group Management Protocol (IGMP) lets host and routers share information about multicast groups
memberships. IGMP snooping is a switch feature that monitors the exchange of IGMP messages and copies them to the CPU
for feature 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 IGMP is also used to periodically check the multicast group for members that are no longer active.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.
Figure 4-3-5-1: Multicast Service