The igmp robust-count command sets the robustness variable of the IGMP querier on an interface.
The undo igmp robust-count command restores the default configuration.
| Parameter | Description | Value |
|---|---|---|
| robust-value | Specifies the robust variable of IGMP. It sets the number of times for retransmitting messages to make up for the packet loss. | The value is an integer that ranges from 2 to 5. |
By default, the robustness variable of the IGMP querier is 2.
The querier is responsible for maintaining IGMP membership on an interface. The robustness variable affects the timeout period of the group membership. The timeout period of the group membership is calculated by using the formula, that is, Timeout period of the group membership = Query interval x Robustness variable + Maximum response time. The robustness variable defines the following values:
The number of times for sending general query messages when the querier starts
When the querier starts, the querier sends general query messages for the number of "robustness variable" times. The sending interval is 1/4 of the interval for sending general query messages. The interval for sending general query messages can be set by using the igmp timer query command or the timer query command.
The number of times for sending IGMPv2 or IGMPv3 group-specific query messages when the querier receives a Leave message
When the querier receives a Leave message for a certain group, the querier sends group-specific messages continuously for the number of "robustness variable" times to check whether any other member of this group exists. The interval for sending group-specific query messages can be set by using the igmp lastmember-queryinterval command or the lastmember-queryinterval command.
The number of times for the querier to send group/source-specific query messages after receiving an IGMPv3 (S, G) Report message.
When receiving an (S, G) Report message, the querier sends group/source-specific Query messages for the "robustness variable" times. The interval for sending group/source-specific Query messages can be set by using the igmp lastmember-queryinterval command or the lastmember-queryinterval command.
The function of this command is the same as that of the robust-count command used in the IGMP view, except for the function range. The configuration in the IGMP view is globally valid in the instance, whereas the configuration in the interface view is valid only for the current interface. The system prefers the configuration in the system view. The configuration in the IGMP view is used only when the configuration in the interface view is not done.
You must run the multicast routing-enable command to enable the multicast function before using the command.