20
Internet Group Management Protocol
(IGMP)
The IGMP commands are supported by the Dell Networking Operating System (OS).
IGMP Snooping Commands
The Dell Networking OS supports IGMP Snooping version 2 and 3 on all Dell Networking systems.
Important Points to Remember for IGMP Snooping
• The Dell Networking OS supports version 1, version 2, and version 3 hosts.
• The Dell Networking OS IGMP snooping implementation is based on IP multicast address (not based
on Layer 2 multicast mac address) and the IGMP snooping entries are in Layer 3 flow table not in
Layer 2 forwarding information base (FIB).
• The Dell Networking OS IGMP snooping implementation is based on draft-ietf-magma-snoop-10.
• IGMP snooping is not enabled by default on the switch.
• A maximum of 1800 groups and 600 virtual local area network (VLAN) are supported.
• IGMP snooping is not supported on a default VLAN interface.
• IGMP snooping is not supported over VLAN-Stack-enabled VLAN interfaces (you must disable IGMP
snooping on a VLAN interface before configuring VLAN-Stack-related commands).
• IGMP snooping does not react to Layer 2 topology changes triggered by spanning tree protocol (STP).
• IGMP snooping reacts to Layer 2 topology changes multiple spanning tree protocol (MSTP) triggers by
sending a general query on the interface that comes in the FWD state.
Important Points to Remember for IGMP Querier
• The IGMP snooping Querier supports version 2.
• You must configure an IP address to the VLAN interface for IGMP snooping Querier to begin. The
IGMP snooping Querier disables itself when a VLAN IP address is cleared, and then it restarts itself
when an IP address is reassigned to the VLAN interface.
• When enabled, IGMP snooping Querier does not start if there is a statically configured multicast
router interface in the VLAN.
• 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.
• When enabled, IGMP snooping Querier periodically sends general queries with an IP source address
of the VLAN interface. If it receives a general query on any of its VLAN member, it checks the IP
source address of the incoming frame.
• If the IP SA in the incoming IGMP general query frame is lower than the IP address of the VLAN
interface, the switch disables its IGMP snooping Querier functionality.
Internet Group Management Protocol (IGMP)
545