H3C Technologies H3C S7500E Series Switches - Manual (Page 121)

5-14
Configuration Prerequisites
Before adjusting IGMP performance, complete the following tasks:
z Configure any unicast routing protocol so that all devices in the domain are interoperable at
the network layer.
z Configure basic functions of IGMP
Before adjusting IGMP performance, prepare the following data:
z Startup query interval
z Startup query count
z IGMP general query interval
z IGMP querier’s robustness variable
z Maximum response time for IGMP general queries
z IGMP last-member query interval
z Other querier present interval
Configuring IGMP Message Options
IGMP queries include group-specific queries and group-and-source-specific queries, and
multicast groups change dynamically, so a device cannot maintain the information for all
multicast sources and groups, For this reason, when receiving a multicast packet but unable to
locate the outgoing interface for the destination multicast group, an IGMP router needs to
leverage the Router-Alert option to pass the multicast packet to the upper-layer protocol for
processing. For details about the Router-Alert option, refer to RFC 2113.
An IGMP message is processed differently depending on whether it carries the Router-Alert
option in the IP header:
z By default, for the consideration of compatibility, the device does not check the
Router-Alert option, namely it processes all the IGMP messages it received. In this case,
IGMP messages are directly passed to the upper layer protocol, no matter whether the
IGMP messages carry the Router-Alert option or not.
z To enhance the device performance and avoid unnecessary costs, and also for the
consideration of protocol security, you can configure the device to discard IGMP messages
that do not carry the Router-Alert option.
Configuring IGMP packet options globally
Follow these steps to configure IGMP packet options globally:
To do... Use the command... Remarks
Enter system view system-view —
Enter public instance IGMP view
or VPN instance IGMP view
igmp [ vpn-instance
vpn-instance-name ]
—
Configure the router to discard
any IGMP message that does
not carry the Router-Alert option
require-router-alert
Optional
By default, the device does not
check the Router-Alert option.