3Com Switch 8800 Advanced Software V5 Configuration Guide

Troubleshooting IGMP 537
Analysis
■ The correctness of networking and interface connections directly affects the
generation of group member information.
■ Multicast routing must be enabled on the device.
■ If the igmp group-policy command has been configured on the POS
interface, the POS interface cannot receive report messages that fail to pass
filtering.
Solution
1 Check that the networking is correct and interface connections are correct.
2 Check that multicast routing is enabled. Carry out the display
current-configuration command to check whether the multicast
routing-enable command has been executed. If not, carry out the multicast
routing-enable command in system view to enable IP multicast routing.
3 Check that the interface is in normal state and the correct IP address has been
configured. Carry out the display igmp interface command to view the interface
information. If no interface information is output, this means the interface is
abnormal. Typically this is because the shutdown command has been executed
on the interface, or the interface connection is incorrect, or no correct IP address
has been configured on the interface.
4 Check that no ACL rule has been configured on the POS interface to restrict the
host from joining the multicast group G. Carry out the display
current-configuration interface command to check whether 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.
Inconsistent
Memberships on Devices
on the Same Subnet
Symptom
Different memberships are maintained on different IGMP devices on the same
subnet.
Analysis
■ A device running IGMP maintains multiple parameters for each interface, and
these parameters influence one another, forming very complicated
relationships. Inconsistent IGMP interface parameter configurations for devices
on the same subnet will surely result in inconsistency of memberships.
■ In addition, although IGMP routers are compatible with hosts, all devices on
the same subnet must run the same version of IGMP. Inconsistent IGMP
versions running on devices on the same subnet will also lead to inconsistency
of IGMP memberships.
Solution
1 Check the IGMP configuration. Carry out the display current-configuration
command to view the IGMP configuration information on the interfaces.
2 Carry out the display igmp interface command on all devices on the same
subnet to check the IGMP-related timer settings. Make sure that the settings are
consistent on all the routers.