Operation Manual – Multicast Protocol
Quidway S5600 Series Ethernet Switches-Release 1510 Chapter 6 IGMP Configuration
Huawei Technologies Proprietary
6-7
Caution:
Each IGMP version cannot be switched to each other automatically. So all the Layer 3
switches on a subnet must be configured to use the same IGMP version.
6.2.2 Configuring IGMP Query Packets
I. IGMP general query packets
The Layer 3 switch sends IGMP general query packets to the connected network
segment periodically to get to know which multicast groups in the network segment
have members according to the returned IGMP report packets. The multicast router
also sends query packets periodically. When it receives the IGMP join packets of a
group member, it will refresh the membership information of the network segment.
II. IGMP group-specific packets
The query router (querier for short) maintains the IGMP joins packets on the interface
on the shared network. After the related features are configured, the IGMP querier will
send IGMP group-specific query packets at the user-defined interval for the
user-defined times when it receives the IGMP leave packets from the hosts.
Suppose a host in a multicast group decides to leave the multicast group. The related
procedure is as follows:
z The host sends an IGMP leave packet.
z When the IGMP querier receives the packet, it will send IGMP group-specific
query packets 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 packet from the querier, they will send IGMP join packets in the maximum
response time specified in the packet.
z If the IGMP querier receives IGMP join packets 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 join packets 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 procedure is only fit for the occasion when IGMP queriers runs IGMP version 2.
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