H3C Technologies H3C S12500 Series Switches - Manual (Page 123)

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# Display IGMP group information on Switch A.
[SwitchA] display igmp group
Total 1 IGMP Group(s).
Interface group report information of VPN-Instance: public net
Vlan-interface100(192.168.1.1):
Total 1 IGMP Groups reported
Group Address Last Reporter Uptime Expires
224.1.1.1 192.168.1.2 00:02:04 00:01:15
The output shows that IGMP reports from the hosts are forwarded to Switch A through the proxy
interface, VLAN-interface 100 on Switch B.
Troubleshooting IGMP
No membership information on the receiver-side switch
Symptom
When a host sends a report for joining multicast group G, no membership information of the multicast
group G exists on the switch closest to that host.
Analysis
• The correctness of networking and interface connections and whether the protocol layer of the
interface is up directly affect the generation of group membership information.
• Multicast routing must be enabled on the switch, and IGMP must be enabled on the interface
connecting to the host.
• If the IGMP version on the router port is lower than that on the host, the switch will not be able to
recognize the IGMP report from the host.
• If the igmp group-policy command has been configured on the interface, the interface cannot
receive report messages that fail to pass filtering.
Solution
1. Check that the networking, interface connection, and IP address configuration are correct. Check
the interface information with the display igmp interface command. If no information is output, the
interface is in an abnormal state. This is usually because you have configured the shutdown
command on the interface, the interface is not correctly connected, or the IP address configuration
is not correctly done.
2. Use the display current-configuration command to verify that the multicast routing-enable
command has been executed. If not, use the multicast routing-enable command in system view to
enable IP multicast routing. In addition, check that IGMP is enabled on the corresponding
interfaces.
3. Use the display igmp interface command to verify that the version of IGMP on the interface is lower
than that on the host.
4. Use the display current-configuration interface command to verify that the igmp group-policy
command has been executed. If the host is restricted from joining the multicast group G, the ACL
rule must be modified to allow receiving the reports for the multicast group G.