R3102-R3103-HP 6600/HSR6600 Routers IP Multicast Configuration Guide

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Command Remarks
3. Configure the maximum
number of multicast groups
that the interface can join.
igmp group-limit limit
The default value is 16384.
The maximum number of multicast groups
that a VLAN interface can join is 1000. If
more than 1000 multicast groups are
configured, only 1000 multicast groups
takes effect.
Adjusting IGMP performance
When you adjust IGMP performance, follow these guidelines:
• The configurations made in IGMP view are effective on all interfaces. The configurations made in
interface view are effective only on the current interface.
• A configuration made in interface view always has priority over the same configuration made in
IGMP view, 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 IGMP functions.
• Determine the startup query interval.
• Determine the startup query count.
• Determine the IGMP general query interval.
• Determine the IGMP querier's robustness variable.
• Determine the maximum response time for IGMP general queries.
• Determine the IGMP last-member query interval.
• Determine the other querier present interval.
Configuring Router-Alert option handling methods
IGMP queries include group-specific queries and group-and-source-specific queries. Multicast groups
change dynamically, so a device cannot maintain the information for all multicast sources and groups.
For this reason, when an IGMP router receives a multicast packet but cannot locate the outgoing interface
for the destination multicast group, it must use the Router-Alert option to pass the multicast packet to the
upper-layer protocol for processing. For more information about the Router-Alert option, see RFC 2113 .
An IGMP message is processed differently depending on whether it carries the Router-Alert option in the
IP header:
• For compatibility, the device by default ignores the Router-Alert option and processes all received
IGMP messages, no matter whether the IGMP messages carry the Router-Alert option.
• To enhance device performance, avoid unnecessary costs, and ensure protocol security, configure
the device to discard IGMP messages that do not carry the Router-Alert option.