The robust-count command sets a global robustness variable for an MLD querier.
The undo robust-count command restores the default robustness variable.
By default, the robustness variable of an MLD querier is 2.
| Parameter | Description | Value |
|---|---|---|
| robust-value | Specifies the robustness variable of an MLD querier. | The value is an integer that ranges from 2 to 5. |
Usage Scenario
The MLD querier robustness variable specifies the retransmission count of MLD packets to minimize the impact of packet loss on the network.
On a shared network segment, a querier maintains MLD group memberships. The robustness variable affects the timeout period of group memberships. The timeout period of the group membership is calculated using the formula:
Timeout period of the group memberships = Interval for sending MLD General Query messages x Robustness variable + Maximum response time
Number of times the querier sends General Query messages when the querier starts
When a querier starts, it sends General Query messages a certain number of times specified by the robustness variable to query the multicast groups that have members on the shared network segment. The interval for sending General Query messages is configured using the mld timer query or timer query (MLD view) command.
Number of times the querier sends Multicast Address Specific Query messages or Multicast Address and Source Specific Query messages
When receiving a Multicast Listener Done message of a multicast group, the querier sends Multicast Address Specific Query messages a certain number of times specified by the robustness variable to check whether the group has members. When the querier receives a Multicast Listener Report message indicating that source-group mapping changes, the querier sends Multicast Address and Source Specific Query messages a certain number of times specified by the robustness variable. The interval for sending Multicast Address Specific Query messages or Multicast Address and Source Specific Query messages is set using the mld lastlistener-queryinterval or lastlistener-queryinterval (MLD view) command.
A larger robustness variable makes an MLD querier more robust but increases the timeout period of group memberships.
Prerequisites
Layer 3 IPv6 multicast has been enabled using the multicast ipv6 routing-enable command in the system view.
Precautions
The function of this command is the same as that of the mld robust-count command used in the interface view. The configuration in the MLD view is globally valid, whereas the configuration in the interface view takes effect only for the current interface. The configuration in the interface view takes precedence over the configuration in the MLD view. The configuration in the MLD view is used only when no configuration is performed in the interface view.