(S, G) entry is not generated on the S series switch configured with IGMP SSM mapping

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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.

Other related questions:
Can S series switches use SSM mapping to convert the version of IGMP messages
Although SSM mapping takes effect only for IGMPv3 messages in a VLAN, the switch does not convert IGMPv2 messages into IGMPv3 messages before sending the messages to router ports. You can configure IGMP snooping proxy or IGMP snooping Report suppression on the switch to enable the switch to send IGMPv3 messages to the upstream device.

Application and support of SSM mapping on an S series switch
The source-specific multicast (SSM) model conserves multicast addresses and is more secure than the any-source multicast (ASM) model. Only IGMPv3 supports SSM. A host running IGMPv3 can specify multicast source addresses in Report messages. Some hosts can only run IGMPv1 or IGMPv2. To enable these hosts to receive the SSM service, multicast devices need to offer the IGMP snooping SSM mapping function. IGMP snooping SSM mapping is a Layer 2 SSM mapping feature used on IPv4 multicast networks. After static SSM mapping entries are configured on a Layer 2 device, the device can convert (*, G) information in IGMPv1 and IGMPv2 Report messages to (S, G) information to provide the SSM service for IGMPv1 and IGMPv2 hosts. S indicates the multicast source, G indicates the multicast group, and the asterisk (*) indicates any multicast source. S series switches excluding the S1700 support IGMP snooping SSM mapping.

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 does an S series switch have a (*,G) entry and an (S,G) entry in the multicast routing table
It is normal that each multicast group has two entries on an S series switch. For ASM multicast services, the (*,G) entry is generated when a switch receives a user request to join the multicast group, and the (S,G) entry is generated when the switch receives multicast data packets for the multicast group. The outbound interface in the (S,G) entry is obtained from the (*,G) entry.

Generation of dynamic DHCP snooping binding entries on S series switch
Information about generating DHCP snooping binding entries is as follows: - When the dhcp snooping enable command is not run on the user-side interface and the network-side interface is not configured as a trusted interface, users can go online, but no DHCP snooping binding entry is generated. - When the dhcp snooping enable command is not run on the user-side interface and the network-side interface is configured as a trusted interface, users can go online, but no DHCP snooping binding entry is generated. - When the dhcp snooping enable command is run on the user-side interface and the network-side interface is not configured as a trusted interface, users cannot go online, but no DHCP snooping binding entry is generated. - When the dhcp snooping disable command is run on the user-side interface, users can go online, but no DHCP snooping binding entry is generated no matter whether the network-side interface is configured as a trusted interface. - When the dhcp snooping enable command is run on the user-side interface and both user-side and network-side interfaces are configured as trusted interfaces, users can go online, but no DHCP snooping binding entry is generated. - If the DHCP snooping function has been enabled but no DHCP snooping entry is generated, you can check the device configuration in the preceding aspects.

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