User's Manual

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When L3 multicast is enabled in multiple switch cascading, the upstream devices can only learn the
downstream vlan ports through the multicast routing protocol and there is no IGMP packet exchange between
the upstream and downstream devices. Hence the snooping of the upstream devices cannot learn the specific
physical ports that the downstream devices connect and the upstream devices will send the multicast packets
to all physical ports in the local vlan. After this command is enabled, the upstream devices can forward the
multicast packets to the physical ports that the downstream devices connect, preventing the multicast packets
to be broadcast in the downstream vlan.
Run the following commands in global configuration mode.
Command Purpose
[
no
]
ip igmp-
snooping forward-
l3-to-mrouter
Sets the forward-l3-to-mrouter function of IGMP-
snooping.
By default, the IGMP-snooping forward-l3-to-mrouter is disabled.
Note:
This command can be used to send the data packets to the multicast routing port, but the switchchip
can limit the source-data-port, so the data packets will not be sent to the port of source data, but to
the downstream multicast routing port that is registered on PIM-SM.
42.1.17 Configuring Sensitive mode and Value for IGMP Snooping
If IGMP snooping’s sensitive mode is enabled, when port in trunk mode is shut down, set router-age time of
mrouter at active status as sensitive value, and send out query message quickly.
Configure the following in the global configuration mode:
Command Purpose
[
no
]
ip igmp-
snooping
sensitive
[value [3-
30] ]
Configuring IGMP-snooping
’
s sensitive and value could be
router-age time of currently active mrouter.
By default IGMP snooping sensitive is disabled.
Note:
When it is sensitive mode, sensitive value is used to update router-age aiming at current one time period. Next
time, route-age is recovered as configured time router-age time.
42.1.18 Configuring IGMP Snooping’s v3-leave-check Function
If IGMP-snooping’s v3-leave-check feature is enabled, send special query message after receiving v3’s leave
message. Otherwise, no operation is processed.
Configure the following in the global configuration mode:
Command Purpose
[
no
]
ip igmp-
Configuring IGMP-snooping
’
s v3-leave-check. Send special