Why does an S series switch fail to generate IGMP group membership entries when receiving IGMP packets

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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.

Other related questions:
Why does an S series switch receive much multicast traffic when IGMP snooping is not configured?
The destination address of these multicast data packets is a multicast group address, of which the MAC address entries cannot be learned on the Layer 2 switch. Therefore, the switch broadcasts the multicast data packets to all the interfaces in the same broadcast domain. All hosts in the broadcast domain will receive the multicast data packets, regardless of whether or not they are members of the multicast group. Much network bandwidth is occupied and multicast traffic is heavy. IGMD snooping solves this preceding problem. With IGMP snooping configured, the Layer 2 switch listens to and analyzes IGMP packets exchanged between multicast users and the upstream router, and creates Layer 2 multicast forwarding entries accordingly. Multicast data packets are then forwarded based on the Layer 2 multicast forwarding entries, instead of being broadcast on the Layer 2 network. Layer 2 multicast is irrelevant to the number of multicast sources. For S series switches excluding the S1700, to enable IGMP snooping in VLAN 10, perform the following configurations: [HUAWEI] igmp-snooping enable //Enable IGMP snooping globally. [HUAWEI] vlan 10 [HUAWEI-vlan10] igmp-snooping enable //Enable IGMP snooping in VLAN 10.

(S, G) entry is not generated on the S series switch configured with IGMP SSM mapping
The switch interface is enabled with SSM mapping and IGMP, and is configured with a static SSM mapping policy. After the interface receives IGMPv1 or IGMPv2 Report messages, no corresponding (S, G) entry exists in the FIB table. A: When a querier receives an IGMPv1 or IGMPv2 (*, G) Report message, the querier checks G. When G is in the SSM group address range and the host is configured with G-related SSM mapping rules, the switch converts (*, G) to (G, Include, (S1, S2, S3�?), implementing SSM mapping. Possible causes are as follows: G in the (*, G) Report message is not in the SSM group address range. Run the display this command in the PIM view to check the configuration. If the command output shows the ssm-policy basic-acl-number or ssm-policy acl-name acl-name command, the SSM group address range is defined on the device. Run the display acl command to check the ACL configuration. Ensure that G is in the SSM group address range. By default, the SSM group address range is 232.0.0.0/8. - The SSM mapping rules related to G in the (*, G) Report message are not configured. Run the display igmp ssm-mapping interface interface-type interface-number command to check the SSM mapping rules configured on the device and check whether the source address of G is specified. Check whether the group address configured with SSM mapping rules is in the SSM group address range.

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

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.


Why does an S series switch fail to generate Layer 3 multicast forwarding entries when receiving multicast data packets with destination IP addresses in the SSM group address range
An S series switch generates Layer 3 multicast forwarding entries for the group addresses in the SSM group address range only when receiving multicast protocol packets. Multicast data packets cannot trigger generation of Layer 3 multicast forwarding entries for such group addresses. Use either of the following methods to solve this problem: - Configure IGMPv3 or SSM mapping on user-side interfaces. When users order multicast programs, they can send IGMP messages with source-group information to trigger generation of Layer 3 multicast forwarding entries. - Configure PIM-SM on downstream devices. When users need to join a specified source-group, they can send PIM messages with source-group information to trigger generation of Layer 3 multicast forwarding entries.

Does an S series switch enabled with IGMP snooping querier participate in IGMP querier election
After IGMP snooping querier is enabled on an S series switch, the switch periodically sends Query messages to users in a VLAN but does not participate in IGMP querier election or forward Query messages to a VLAN. Layer 2 multicast querier is used when the switch connects to no upstream Layer 3 device or when the IGMP querier function is not enabled on the upstream Layer 3 device. If an IGMP querier exists on the network, do not enable the IGMP snooping querier function on the switch. This is because this function affects querier election on the upstream Layer 3 device and causes multicast service failures.

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