Troubleshooting IGMP Snooping Configuration 577
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.
Analysis
■ The ACL rule is incorrectly configured.
■ The multicast group policy is not correctly applied.
■ The function of dropping unknown multicast data is not enabled, so unknown
multicast data is flooded.
■ Certain ports have been configured as static member ports of multicasts
groups, and this configuration conflicts with the configured multicast group
policy.
Solution
1 Use the display acl command to check the configured ACL rule. Make sure that
the ACL rule conforms to the multicast group policy to be implemented.
2 Use the display this command in IGMP Snooping view or in the corresponding
interface view to check whether the correct multicast group policy has been
applied. If not, use the group-policy or igmp-snooping group-policy command
to apply the correct multicast group policy.
3 Use the display current-configuration command to check whether the function
of dropping unknown multicast data is enabled. If not, use the igmp-snooping
drop-unknown command to enable the function of dropping unknown multicast
data.
4 Use the display igmp-snooping group command to check whether any port has
been configured as a static member port of any multicast group. If so, check
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