H3C S7500 Series Ethernet Switches Operation Manual

Operation Manual – Multicast
H3C S7500 Series Ethernet Switches Chapter 6
IGMP Configuration
6-7
z When the IGMP querier receives the message, it will send IGMP group-specific
query messages at the interval configured by the igmp
lastmember-queryinterval command (the interval is 1 second by default) for the
robust-value times (the robust-value argument is configured by the igmp
robust-count command and it is 2 by default).
z If other hosts are interested in the group after receiving the IGMP group-specific
query message from the querier, they will send IGMP report messages in the
maximum response time specified in the message.
z If the IGMP querier receives IGMP join messages from other hosts within the
robust-value x seconds time, it will maintain the membership of the group.
z If the IGMP querier does not receive IGMP report messages from other hosts after
the robust-value x seconds time, it considers the group times out and will not
maintain the membership of the group.
The procedures are only applicable to the occasion where IGMP queriers run IGMPv2.
If the host runs IGMPv1, it does not send IGMP leave messages when leaving a group,
so the conditions will not be the same as described in the procedures above.
III. IGMP querier substitution rules
The lifetime of an IGMP querier is limited. If the former querier does not send query
messages in the specified time, another router will replace the IGMP querier.
IV. The maximum query time of IGMP messages
When the host receives a query message, it will set a timer for each of its multicast
groups. The timer value is selected from 0 to the maximum response time at random.
When the value of a timer decreases to 0, the host will send the membership
information of the multicast group.
Through configuring the reasonable maximum response time, you can enable the host
to respond to the query messages quickly and enable the Layer 3 switch to know the
membership information of each multicast group quickly.
Follow these steps to configure IGMP query messages:
To do... Use the command... Remarks
Enter system view system-view —
Enable the multicast
routing protocol
multicast
routing-enable
Enable the multicast
routing protocol.
Enter VLAN interface view
interface Vlan-interface
interface-number
—