Adjusting IGMP Performance 1123Adjusting IGMPPerformancen For the configuration tasks described in this section■ Configurations performed in IGMP view are effective on all interfaces, whileconfigurations performed in interface view are effective on the currentinterface only.■ If the same feature is configured in both IGMP view and interface view, theconfiguration performed in interface view is given priority, regardless of theconfiguration sequence.ConfigurationPrerequisitesBefore adjusting IGMP performance, complete the following tasks:■ Configure any unicast routing protocol so that all devices in the domain areinteroperable at the network layer.■ Configure basic functions of IGMP.Before adjusting IGMP performance, prepare the following data:■ IGMP general query interval■ IGMP querier’s robustness variable■ Maximum response time for IGMP general queries■ IGMP last-member query interval■ Other querier present intervalConfiguring IGMPMessage OptionsAs there are IGMP group-specific and group-and-source-specific queries, andmulticast groups change dynamically, a device cannot join all multicast groups.Therefore, when receiving a multicast packet but unable to locate the outgoinginterface for the destination multicast group, an IGMP router needs to leveragethe Router-Alert option to pass the multicast packet to the upper-layer protocol forprocessing. For details about Router-Alert, refer to RFC 2113.Depending on whether an IGMP message carries the Router-Alert option in the IPheader, the device processes the message differently:■ For the consideration of compatibility, the device does not check theRouter-Alert option, namely it processes all the IGMP messages it received. Inthis case, IGMP messages are directly passed to the upper layer protocol, nomatter whether the IGMP messages carry the Router-Alert option or not.■ To enhance the device performance and avoid unnecessary costs, and also forthe consideration of protocol security, you can configure the device to discardIGMP messages that do not carry the Router-Alert option.Configuring IGMP packet options globallyFollow these steps to configure IGMP packet options globally:To do... Use the command... DescriptionEnter system view system-view -
