Enabling Igmp Snooping Querier - HP A8800 Configuration Manual

Enabling IGMP snooping querier

In an IP multicast network that runs IGMP, a multicast router or Layer 3 multicast switch sends IGMP
queries, so that all Layer 3 multicast devices can establish and maintain multicast forwarding entries, in
order to forward multicast traffic correctly at the network layer. This router or Layer 3 switch is called the
"IGMP querier." For more information about IGMP querier, see
However, a Layer 2 multicast switch does not support IGMP, and therefore cannot send general queries
by default. To establish and maintain multicast forwarding entries at the data link layer, you can
configure the Layer 2 device in a VLAN as an IGMP snooping querier on a network where no Layer 3
multicast devices are present. In this way, the Layer 2 device sends IGMP queries.
To enable IGMP snooping querier:
Step
Enter system view.
1.
2. Enter VLAN view.
3. Enable IGMP snooping
querier.
NOTE:
Do not configure an IGMP snooping querier in a multicast network running IGMP. Although an IGMP
snooping querier does not take part in IGMP querier elections, it may affect IGMP querier elections
because it sends IGMP general queries with a low source IP address.
Configuring parameters for IGMP queries and responses
You can modify the IGMP general query interval based on 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 time 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 properly set the maximum response delay.
The maximum response delay for IGMP general queries is set by the max-response-time command.
•
• The maximum response delay for IGMP group-specific queries equals the IGMP last-member query
interval.
IMPORTANT:
Make sure the interval for sending IGMP general queries is larger than the maximum response delay for
IGMP general queries. Otherwise, multicast group members might be deleted by mistake.
Configuring the global parameters for IGMP queries and responses
Step
1. Enter system view.
Command
system-view
vlan vlan-id
igmp-snooping querier
Command
system-view
26
"Configuring IGMP."
Remarks
N/A
N/A
Disabled by default.
Remarks
N/A