shutdown
Dell(conf-if-vl-100)#
Disabling Multicast Flooding
If the switch receives a multicast packet that has an IP address of a group it has not learned (unregistered
frame), the switch floods that packet out of all ports on the VLAN.
When you configure the no ip igmp snooping flood command, the system drops the packets
immediately. The system does not forward the frames on mrouter ports, even if they are present. Disable
Layer 3 multicast (no ip multicast-routing) in order to disable multicast flooding.
• Configure the switch to only forward unregistered packets to ports on a VLAN that are connected to
mrouter ports.
CONFIGURATION mode
no ip igmp snooping flood
Specifying a Port as Connected to a Multicast Router
To statically specify or view a port in a VLAN, use the following commands.
• Statically specify a port in a VLAN as connected to a multicast router.
INTERFACE VLAN mode
ip igmp snooping mrouter
• View the ports that are connected to multicast routers.
EXEC Privilege mode.
show ip igmp snooping mrouter
Configuring the Switch as Querier
To configure the switch as a querier, use the following command.
Hosts that do not support unsolicited reporting wait for a general query before sending a membership
report. When the multicast source and receivers are in the same VLAN, multicast traffic is not routed and
so there is no querier. Configure the switch to be the querier for a VLAN so that hosts send membership
reports and the switch can generate a forwarding table by snooping.
• Configure the switch to be the querier for a VLAN by first assigning an IP address to the VLAN
interface.
INTERFACE VLAN mode
ip igmp snooping querier
IGMP snooping querier does not start if there is a statically configured multicast router interface in the
VLAN.
The switch may lose the querier election if it does not have the lowest IP address of all potential
queriers on the subnet.
When enabled, IGMP snooping querier starts after one query interval in case no IGMP general query
(with IP SA lower than its VLAN IP address) is received on any of its VLAN members.
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Internet Group Management Protocol (IGMP)
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