Dell PowerEdge FX2/FX2s - Manual (Page 87)

Figure 14. IGMP Membership Queries: Leaving and Staying in Groups
IGMP Snooping
IGMP snooping is auto-configured on an Aggregator.
Multicast packets are addressed with multicast MAC addresses, which represents a group of devices
rather than one unique device. Switches forward multicast frames out of all ports in a VLAN by default,
even if there are only a small number of interested hosts, resulting in a waste of bandwidth. IGMP
snooping enables switches to use information in IGMP packets to generate a forwarding table that
associate ports with multicast groups, so that the received multicast frames are forwarded only to
interested receivers.
How IGMP Snooping is Implemented on an Aggregator
• IGMP snooping is enabled by default on the switch.
• Dell Networking OS supports version 1, version 2 and version 3 hosts.
• Dell Networking OS — IGMP snooping is based on the IP multicast address (not on the Layer 2
multicast MAC address). IGMP snooping entries are stored in the Layer 3 flow table instead of in the
Layer 2 forwarding information base (FIB).
• Dell Networking OS — IGMP snooping is based on draft-ietf-magma-snoop-10.
• A maximum of 2k groups and 4k virtual local area networks (VLAN) are supported.
• IGMP snooping is not supported on the default VLAN interface.
• Flooding of unregistered multicast traffic is enabled by default.
• Queries are not accepted from the server side ports and are only accepted from the uplink LAG.
• Reports and Leaves are flooded by default to the uplink LAG irrespective of whether it is an mrouter
port or not.
Displaying IGMP Information
Use the show commands from the below table, to display information on IGMP. If you specify a group
address or interface:
• Enter a group address in dotted decimal format; for example, 225.0.0.0.
• Enter an interface in one of the following formats: tengigabitethernet slot/port, port-
channel port-channel-number, or vlan vlan-number.
IGMP Overview 87