Why is no information about members of an IGMP multicast group displayed in the display igmp group command output on a CE series switch

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If the display igmp group command output does not display any information, the specified multicast group has no members.


In normal cases, after users join a multicast group dynamically by sending IGMP Report messages, the IGMP multicast group information is displayed in the display igmp group command output. The following is an example:
<HUAWEI> display igmp group
Interface group report information of VPN instance: public net
Vlanif100(10.1.6.2):
Total 1 IGMP Group reported
Group Address Last Reporter Uptime Expires
225.1.1.2 10.1.6.10 00:02:04 00:01:17


In the command output, Group Address indicates the IP address of the multicast group that users have joined, and Last Reporter indicates the last host that has sent an IGMP Report message.



Other related questions:
No information is displayed when IGMP snooping is enabled on an S series switch
For S series switches excluding the S1700, the display igmp-snooping command displays information about an IGMP snooping enabled VLAN. The command displays information only when the following conditions are met: - IGMP snooping has been enabled in the VLAN. - The VLAN is in Up state and at least one interface in the VLAN is Up.

How does an IGMP-enabled S series switch determine whether a member host exists in the multicast group
In IGMPv1 on S series switches, hosts leave their multicast groups without sending Leave messages. The device uses IGMP group entries timer to determine the whether all multicast group members in the network segment have left. In IGMPv2 and IGMPv3, hosts send Leave messages when leaving their group. After receiving the Done message, the querier sends a Group-Specific or a Source-Specific Query message to the network segment. The destination address of the Query message is the address of the multicast group and the group address in the message is also filled in with the address of the multicast group. If other members of the group exist on the network segment, they respond with Report messages. If no response is received when the timeout period ends, the querier considers that no member of the group exists on the network segment and cancels forwarding multicast data to the group.

Why does an S series switch fail to generate IGMP group membership entries when receiving IGMP packets
If an S series switch cannot generate entries, the possible causes are as follows: The version of received IGMP messages is later than the IGMP version configured on the switch. Solution: Run the display igmp interface interface-type interface-num command to check the IGMP version on the interface receiving the IGMP messages. If the IGMP version on the interface is earlier than the version of received IGMP messages, run the igmp version version command in the interface view to set a later IGMP version. The interface receives IGMPv1 or IGMPv2 messages with addresses in the SSM group address range, but SSM mapping is not configured on the switch. Solution: Check whether the group address in the received IGMP messages is in the SSM group address range. If so, run the igmp ssm-mapping enable command in the interface view to enable SSM mapping, and then run the ssm mapping group-address mask source-address command in the IGMP view to configure SSM mapping entries matching the IGMP messages. The group address in received IGMP packets is the reserved group address. The group addresses in the range of 224.0.0.1 to 224.0.0.255 are reserved for protocols. When receiving IGMP Report messages with destination addresses in this range, the switch does not generate IGMP group membership entries.

Why cannot fan information be displayed in the display device command output and why is the ALM indicator of AC power yellow when the S7700&S9700's fan is operating
The monitoring unit (MCU or CMU) fails to communicate with the fan or AC power supply. NOTE: If you need to buy the CMU, contact Huawei local office.

Whether it is normal that the output of the display hrp group command displays that the status of certain groups is disable in hot standby deployment
It is normal. In hot standby deployment, only the active VGMP group on the active device is working, and only the standby VGMP group on the standby device is working.

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