Users Guide

IGMP Snooping Commands
Dell Networking OS supports IGMP Snooping version 2 and 3 on all Dell Networking systems.
Important Points to Remember for IGMP
Snooping
• Dell Networking OS supports version 1, version 2, and version 3 hosts.
• 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).
• Dell Networking OS IGMP snooping implementation is based on draft-ietf-magma-snoop-10.
• Dell Networking OS supports IGMP snooping on JUMBO-enabled cards.
• IGMP snooping is not enabled by default on the switch.
• A maximum of 1800 groups and 600 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.
If the IP SA of the incoming IGMP general query is higher than the VLAN IP address, the switch continues
to work as an IGMP snooping Querier.
Internet Group Management Protocol (IGMP) 838