R3303-HP HSR6800 Routers IP Multicast Configuration Guide

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Configuration prerequisites
Before you configure IGMP snooping querier, complete the following tasks:
• Enable IGMP snooping in the VLAN.
• Determine the interval for sending IGMP general queries.
• Determine the IGMP last-member query interval.
• Determine the maximum response delay for IGMP general queries.
• Determine the source address of IGMP general queries.
• Determine the source address of IGMP group-specific queries.
Enabling IGMP snooping querier
In an IP multicast network that runs IGMP, a Layer 3 multicast device sends IGMP queries. This allows all
Layer 3 multicast devices to establish and maintain multicast forwarding entries for forwarding multicast
traffic correctly at the network layer. This Layer 3 multicast device is called the "IGMP querier".
A Layer 2 multicast device does not support IGMP, and therefore cannot send general queries by default.
When you configure an IGMP snooping querier on a Layer 2 multicast device in a VLAN where multicast
traffic is switched only at Layer 2 and no multicast routers are present, the Layer 2 multicast device sends
IGMP queries, so that multicast forwarding entries can be established and maintained at the data link
layer.
It is meaningless to configure an IGMP snooping querier in a multicast network that runs IGMP. Although
an IGMP snooping querier does not take part in IGMP querier elections, it might affect IGMP querier
elections because it sends IGMP general queries with a low source IP address. For more information
about IGMP querier, see "Configuring IGMP."
To enable IGMP snooping querier in a VLAN:
Ste
p
Command Remarks
1. Enter system view.
system-view N/A
2. Enter VLAN view.
vlan vlan-id N/A
3. Enable IGMP snooping
querier.
igmp-snooping querier Disabled by default.
Configuring parameters for IGMP queries and responses
You can modify the IGMP general query interval based on the actual condition of the network.
A multicast listening host starts a timer for each multicast group that it has joined when it receives an
IGMP query (general query or group-specific query). This timer is initialized to a random value in the
range of 0 to the maximum response delay advertised in the IGMP query message. When the timer value
decreases to 0, the host sends an IGMP report to the multicast group.
To speed up the response of hosts to IGMP queries and avoid simultaneous timer expirations causing
IGMP report traffic bursts, you must correctly set the maximum response delay.
• The maximum response delay for IGMP general queries is set by the max-response-time command.