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

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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.

Other related questions:
Why is no Layer 3 multicast forwarding entry generated on S series switches after users order multicast programs
The possible causes are as follows: - No RP is configured on the PIM-SM network. In this case, configure static or dynamic RP. - The route to the multicast source or RP is unreachable. In this case, configure a unicast routing protocol to enable the switch to learn the routes to the multicast source or RP.

Does an AR learn the source MAC address of multicast packets
The AR learns MAC addresses of received multicast packets.

Can an S series switches forward a packet if both the source and destination IP addresses of the packet are multicast addresses
The S5710-C-LI or S5700SI drops packets whose source and destination IP addresses are both multicast addresses. Other switches broadcast such packets in a VLAN.

Can an S series switch accurately forward multicast data packets if only Layer 3 multicast is configured
For S series switches, Layer 3 multicast protocols can identify only Layer 3 VLANIF interfaces. If only Layer 3 multicast is configured and Layer 2 multicast is not enabled, multicast data is replicated on a VLANIF interface and broadcast in the corresponding VLAN, but cannot be forwarded to an accurate physical interface. When Layer 2 multicast is enabled in the VLAN corresponding to the VLANIF interface, multicast data can be accurately forwarded through a Layer 2 interface.

Why does an S series switch generates Layer 2 multicast forwarding entries in only one VLAN
After an S series switch receives Report messages from the same multicast group in different VLANs, Layer 2 multicast entries are generated in only the VLAN where Report messages are generated first. The causes are as follows: An S5700SI switch running a version earlier than V200R005 or an S5710-C-LI does not generate the same multicast forwarding entry for a multicast group in multiple VLANs. That is, a multicast group can have a forwarding entry only in one VLAN. To solve this problem, configure a multicast VLAN so that multicast data can be distributed to user VLANs through the multicast VLAN. - The preceding restriction does not apply to the S5700SI, S5710-X-LI, S5700S-28X-LI-AC, S5700S-52X-LI-AC, S5720S-SI, S5720SI, and E600 running V200R005 and later versions. These switches, however, cannot generate the same multicast forwarding entry for a multicast group in multiple multicast VLANs. That is, a multicast group can have a forwarding entry only in one multicast VLAN. - The S2700 does not allow an interface to function as the outbound interface of the same multicast forwarding entry in multiple VLAN. That is, one interface can function as the outbound interface of a multicast group in only one VLAN. To solve this problem, add each interface to only one VLAN so that a multicast group has different outbound interfaces in different VLANs.

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