igmp-snooping robust-count
Function
The igmp-snooping robust-count command sets the IGMP robustness variable in a VLAN, which specifies how many times IGMP Query messages are sent.
The undo igmp-snooping robust-count command restores the default IGMP robustness variable in a VLAN.
By default, the robustness variable in a VLAN is 2.
Usage Guidelines
Usage Scenario
Setting IGMP snooping parameters helps improve multicast forwarding performance. By setting the IGMP robustness variable, you can:
Specify the number of times the querier sends a Group-Specific Query message, which prevents packet loss on the network.
When receiving an IGMP Leave message for a multicast group, the wireless access controller sends a Group-Specific Query message certain times (specified by the IGMP robustness variable) to check whether this group has any other members. If the quality of transmission links is low, increase the IGMP robustness variable.
Change the aging time of multicast group member ports.
When receiving an IGMP Report message from a host, the wireless access controller starts the aging timer for the member port. The aging time is calculated using the following formula: Aging time = IGMP robustness variable x General query interval + Maximum response time for General Query messages. The igmp-snooping robust-count command sets the general query count.
Prerequisites
IGMP snooping has been enabled globally using the igmp-snooping enable (system view) command.
Follow-up Procedure
- Run the igmp-snooping query-interval command to set the interval at which General Query messages are sent.
- Run the igmp-snooping max-response-time command to set the maximum response time for General Query messages.
- Run the igmp-snooping lastmember-queryinterval command to set the interval at which Group-Specific Query messages are sent.
Precautions
The configuration takes effect only after you run the igmp-snooping enable (VLAN view) command to enable IGMP snooping in the VLAN.
