620 CHAPTER 46: IGMP CONFIGURATION
n
■ Before you can configure an interface of a PIM-SM device as a static member
of a multicast group, if the interface is PIM-SM enabled, it must be a PIM-SM
DR; if this interface is IGMP enabled but not PIM-SM enabled, it must be an
IGMP querier.
■ As a static member of a multicast group, an interface does not respond to the
queries from the IGMP querier, nor does it send an unsolicited IGMP
membership report or an IGMP leave group message when it joins or leaves a
multicast group. In other words, the interface will not become a real member
of the multicast group.
Configuring a Multicast
Group Filter
You can configure a multicast group filter in IGMP Snooping. For details, see
“Configuring a Multicast Group Filter” on page 566.
Adjusting IGMP
Performance
n
For the configuration tasks described in this section
■ Configurations performed in IGMP view are effective on all interfaces, while
configurations performed in interface view are effective on the current
interface only.
■ If the same feature is configured in both IGMP view and interface view, the
configuration performed in interface view is given priority, regardless of the
configuration sequence.
Configuration
Prerequisites
Before adjusting IGMP performance, complete the following tasks:
■ Configure any unicast routing protocol so that all devices in the domain are
interoperable 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 interval
Configuring IGMP
Message Options
As IGMPv2 and IGMPv3 involve group-specific and group-and-source-specific
queries, and multicast groups change dynamically, a device cannot join all
multicast groups. Therefore, 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 whether it carries the
Router-Alert option in the IP header:
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