Enabling Igmp Immediate-Leave; Igmp Snooping; Igmp Snooping Implementation Information - Dell C9000 Series Networking Configuration Manual

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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

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

View the enable status of the IGMP immediate leave feature.

EXEC Privilege mode

show ip igmp interface

View the enable status of this feature using the command from EXEC Privilege mode, as shown in the

Selecting an IGMP

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 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 Networking recommends that users enable IGMP

snooping on server-facing end-point VLANs only.

Internet Group Management Protocol (IGMP)