H3C Technologies H3C S12500 Series Switches - Manual (Page 109)

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initialized to a random value in the range of 0 to the maximum response delay advertised in the IGMP
query. When the timer value decreases to 0, the host sends an IGMP report to the corresponding
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.
• The maximum response delay for IGMP group-specific queries and IGMP group-and-source-specific
queries equals the IGMP last-member query interval.
When multiple multicast routers exist on the same subnet, the IGMP querier is responsible for sending
IGMP queries. If a non-querier router receives no IGMP query from the querier when the other querier
present interval expires, it considers that the querier as having failed and starts a new querier election.
Otherwise, the non-querier router resets the other querier present timer.
Configuration guidelines
• To avoid frequent IGMP querier changes, set the other querier present interval greater than the
IGMP general query interval.
• To avoid incorrect multicast group member removals, set the IGMP general query interval greater
than the maximum response time for IGMP general queries.
• The configurations of the maximum response time for IGMP general queries, the IGMP last member
query interval, and the IGMP other querier present interval take effect on only IGMPv2 and
IGMPv3.
Configuration procedure
To configure IGMP query and response parameters globally:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter public network IGMP
view or VPN instance IGMP
view.
igmp [ vpn-instance
vpn-instance-name ]
N/A
3. Configure the IGMP querier's
robustness variable.
robust-count robust-value
2 by default.
A higher robustness variable
makes the IGMP querier more
robust, but results in longer
multicast group timeout time.
4. Configure the startup query
interval.
startup-query-interval interval
By default, the startup query
interval is one-quarter of the "IGMP
general query interval."
5. Configure the startup query
count.
startup-query-count value
By default, the startup query count
is the same as the IGMP querier's
robustness variable.
6. Configure the IGMP general
query interval.
timer query interval 60 seconds by default.
7. Configure the maximum
response delay for IGMP
general queries.
max-response-time interval 10 seconds by default.