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When IGMP snooping is enabled in a switch it analyses all the IGMP packets between hosts
connected to the switch and multicast routers in the network. When a switch hears an IGMP
report from a host for a given multicast group, the switch adds the host's port number to the
multicast list for that group. And, when the switch hears an IGMP Leave, it removes the
host's port from the table entry.
IGMP snooping can very effectively reduce multicast traffic from streaming and other
bandwidth intensive IP applications. A switch using IGMP snooping will only forward
multicast traffic to the hosts interested in that traffic. This reduction of multicast traffic
reduces the packet processing at the switch (at the cost of needing additional memory to
handle the multicast tables) and also reduces the workload at the end hosts since their
network cards (or operating system) will not have to receive and filter all the multicast traffic
generated in the network.
Command / Example
Parameter
Description
Switch(config)# ip igmp
snooping
Enable IGMP snooping function.
Switch(config)# ip igmp
snooping aging-time
[1-6000] /10
sec.
Specify the IGMP querier aging time.
If the switch does not receive join
packets from the end device within the
specified time, the entry associated
with this end device will be removed
from the IGMP table.
No command
Switch(config)# no ip igmp snooping
Disable IGMP snooping function.
Switch(config)# no ip igmp snooping aging time
Remove IGMP querier aging time
setting.
Show command
Switch(config)# show ip igmp snooping
Show current IGMP snooping status
including immediate leave function.
Switch(config)# show ip igmp snooping groups
Show IGMP group table. When IGMP
Snooping is enabled, the Switch is
able to read multicast group IP and
the corresponding MAC address from
IGMP packets that enter the device.
Summary of Contents for HES-3109 Series
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