LevelOne GSW-4876 - Manual (Page 147)

C HAPTER 4 | Configuring the Switch
IGMP Snooping
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◆ Proxy Enabled – Enables IGMP Snooping with Proxy Reporting.
(Default: Disabled)
When proxy reporting is enabled with this command, the switch
performs “IGMP Snooping with Proxy Reporting” (as defined in DSL
Forum TR-101, April 2006), including report suppression, last leave,
and query suppression.
Report suppression intercepts, absorbs and summarizes IGMP reports
coming from downstream hosts. Last leave sends out a proxy query
when the last member leaves a multicast group, and query suppression
means that neither specific queries nor general queries are forwarded
from an upstream multicast router to hosts downstream from this
device.
When proxy reporting is disabled, all IGMP reports received by the
switch are forwarded natively to the upstream multicast routers.
Port Related Configuration
◆ Port – Port identifier.
◆ Router Port - Sets a port to function as a router port, which leads
towards a Layer 3 multicast device or IGMP querier. (Default: Disabled)
If IGMP snooping cannot locate the IGMP querier, you can manually
designate a port which is connected to a known IGMP querier (i.e., a
multicast router/switch). This interface will then join all the current
multicast groups supported by the attached router/switch to ensure
that multicast traffic is passed to all appropriate interfaces within the
switch.
◆ Fast Leave - Immediately deletes a member port of a multicast service
if a leave packet is received at that port. (Default: Disabled)
The switch can be configured to immediately delete a member port of a
multicast service if a leave packet is received at that port and the Fast
Leave function is enabled. This allows the switch to remove a port from
the multicast forwarding table without first having to send an IGMP
group-specific (GS) query to that interface.
If Fast Leave is not used, a multicast router (or querier) will send a
GS-query message when an IGMPv2/v3 group leave message is
received. The router/querier stops forwarding traffic for that group only
if no host replies to the query within the specified timeout period.
If Fast Leave is enabled, the switch assumes that only one host is
connected to the interface. Therefore, Fast Leave should only be
enabled on an interface if it is connected to only one IGMP-enabled
device, either a service host or a neighbor running IGMP snooping.
Fast Leave is only effective if IGMP snooping is enabled, and IGMPv2 or
IGMPv3 snooping is used.
Fast Leave does not apply to a port if the switch has learned that a
multicast router is attached to it.
Fast Leave can improve bandwidth usage for a network which
frequently experiences many IGMP host add and leave requests.