Administrator Guide

show config
DellEMC(conf-if-vl-100)#show config
!
interface Vlan 100
no ip address
ip igmp snooping fast-leave
shutdown
DellEMC(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.
Adjusting the Last Member Query Interval
To adjust the last member query interval, use the following command.
When the querier receives a Leave message from a receiver, it sends a group-specific query out of the ports specified in the forwarding
table. If no response is received, it sends another. The amount of time that the querier waits to receive a response to the initial query
before sending a second one is the last member query interval (LMQI). The switch waits one LMQI after the second query before
removing the group-port entry from the forwarding table.
• Adjust the last member query interval.
INTERFACE VLAN mode
Internet Group Management Protocol (IGMP)
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