Users Guide

ipv6 mld query-max-response-time
● Adjust the last member query interval.
INTERFACE mode
ip igmp last-member-query-interval
● Adjust the amount of time the querier waits, for the initial query response, before sending the next IPv6 query.
Interface mode
ipv6 mld last-member-query-interval
Enabling IGMP Immediate-Leave
If the querier does not receive a response to a group-specific or group-and-source query, it sends another (querier robustness
value). Then, after no response, it removes the group from the outgoing interface for the subnet.
IGMP immediate leave reduces leave latency by enabling a router to immediately delete the group membership on an interface
after receiving a Leave message (it does not send any group-specific or group-and-source queries before deleting the entry).
● Configure the system for IGMP immediate leave.
ip igmp immediate-leave
● Configure the system to immediately delete the IPv6 group membership on an interface after receiving a leave message.
ipv6 mld immediate-leave
● View the enable status of the IGMP immediate leave feature.
EXEC Privilege mode
show ip igmp interface
show ipv6 mld interface
View the enable status of this feature using the command from EXEC Privilege mode, as shown in the example in Selecting an
IGMP Version.
IGMP Snooping
IGMP snooping enables switches to use information in IGMP packets to generate a forwarding table that associates ports with
multicast groups so that when they receive multicast frames, they can forward them only to interested receivers.
Multicast packets are addressed with multicast MAC addresses, which represent a group of devices, rather than one unique
device. Switches forward multicast frames out of all ports in a virtual local area network (VLAN) by default, even though there
may be only some interested hosts, which is a waste of bandwidth.
If you enable IGMP snooping on a VLT unit, IGMP snooping dynamically learned groups and multicast router ports are made to
learn on the peer by explicitly tunneling the received IGMP control packets.
IGMP Snooping Implementation Information
● IGMP snooping on Dell EMC Networking OS uses IP multicast addresses not MAC addresses.
● IGMP snooping reacts to spanning tree protocol (STP) and multiple spanning tree protocol (MSTP) topology changes by
sending a general query on the interface that transitions to the forwarding state.
● If IGMP snooping is enabled on a PIM-enabled VLAN interface, data packets using the router as an Layer 2 hop may be
dropped. To avoid this scenario, Dell EMC Networking recommends that users enable IGMP snooping on server-facing end-
point VLANs only.
Configuring IGMP Snooping
Configuring IGMP snooping is a one-step process. To enable, view, or disable IGMP snooping, use the following commands.
There is no specific configuration needed for IGMP snooping with virtual link trunking (VLT). For information about VLT
configurations, refer to Virtual Link Trunking (VLT).
● Enable IGMP snooping on a switch.
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Internet Group Management Protocol (IGMP)