H3C Technologies H3C S3100V2 Series Switches - Manual (Page 57)

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The output shows that Ethernet 1/0/3 on Switch B has joined 224.1.1.1 but not 224.1.1.2.
Assume that Source 2 starts sending multicast traffic to 224.1.1.1. Use the display multicast
forwarding-table to display the multicast forwarding table information.
# Display the information about 224.1.1.1 in the multicast forwarding table on Switch A.
[SwitchA] display multicast forwarding-table 224.1.1.1
Multicast Forwarding Table
Total 1 entry
Total 1 entry matched
00001. (1.1.1.1, 224.1.1.1)
MID: 0, Flags: 0x0:0
Uptime: 00:08:32, Timeout in: 00:03:26
Incoming interface: Vlan-interface101
List of 1 outgoing interfaces:
1: Vlan-interface104
Matched 19648 packets(20512512 bytes), Wrong If 0 packets
Forwarded 19648 packets(20512512 bytes)
The output shows that Switch A maintains a multicast forwarding entry for multicast packets from Source
1 to 224.1.1.1. No forwarding entry exists to forward packets from Source 2 to 224.1.1.1, which indicates
that multicast packets from Source 2 are blocked.
Troubleshooting IGMP snooping configuration
Switch fails in layer 2 multicast forwarding
Symptom
A switch fails to implement Layer 2 multicast forwarding.
Analysis
IGMP snooping is not enabled.
Solution
1. Enter the display current-configuration command to view the running status of IGMP snooping.
2. If IGMP snooping is not enabled, use the igmp-snooping command to enable IGMP snooping
globally, and then use igmp-snooping enable command to enable IGMP snooping in VLAN view.
3. If IGMP snooping is disabled only for the corresponding VLAN, just use the igmp-snooping enable
command in VLAN view to enable IGMP snooping in the corresponding VLAN.
Configured multicast group policy fails to take effect
Symptom
Although a multicast group policy has been configured to allow hosts to join specific multicast groups, the
hosts can still receive multicast data addressed to other multicast groups.