Troubleshooting IGMPv3 Backwards Compatibility

If you configure the switch to operate in v2-v3 compatibility mode, the switch supports all IGMPv2 and v3 messages. The switch parses the group address of the messages. If the group address is out of SSM range and it is a v3 message, the switch drops the message. If it is a v2 message, IGMP snoop processes handle the message.

To troubleshoot issues with the IGMPv3 backwards compatibility feature, perform the following procedure.

Procedure

Enter Privileged EXEC mode:

enable
Verify that the SSM static channel is configured for the v1/v2 joins received. Display the configured SSM static channels:

show ip igmp ssm-map
Verify that the SSM group range is configured for the v1/v2 joins received. Display the configured SSM group range:

show ip igmp ssm

Example

Display the configured SSM static channels and display the configured SSM group range:

Switch:>enable
Switch:1#show ip igmp ssm-map

================================================================================
                                Igmp Ssm Channel
================================================================================
GROUP           SOURCE          MODE       ACTIVE     STATUS
--------------------------------------------------------------------------------
233.252.0.1       192.0.2.200 dynamic    false      enabled
233.252.0.2       192.0.2.200 dynamic    false      enabled
233.252.0.3       192.0.2.200 dynamic    false      enabled
233.252.0.4       192.0.2.200 dynamic    false      enabled
233.252.0.5       192.0.2.200 dynamic    false      enabled
233.252.0.6       192.0.2.200 dynamic    false      enabled
233.252.0.7       192.0.2.200 dynamic    false      enabled
233.252.0.8       192.0.2.200 dynamic    false      enabled
233.252.0.9       192.0.2.200 dynamic    false      enabled
233.252.0.10      192.0.2.200 dynamic    false      enabled

10 out of 10 entries displayed

Switch:1(config)#show ip igmp ssm

================================================================================
                         Igmp Ssm Global - GlobalRouter
================================================================================
DYNAMIC LEARNING     SSM GROUP RANGE
--------------------------------------------------------------------------------
enable               233.252.0.0/255.0.0.0

Job Aid

The following table shows the field descriptions for the show ip igmp ssm-map command.

Table 1. show ip igmp ssm-map command
Field	Description
GROUP	Indicates the IP multicast group address that uses the default range of 232/8.
SOURCE	Indicates the IP address of the source that sends traffic to the group source.
MODE	Indicates that the entry is a statically configured entry (static) or a dynamically learned entry from IGMPv3 (dynamic).
ACTIVE	Indicates the activity on the corresponding source and group. If the source is active and traffic is flowing to the switch, this status is active; otherwise, it is nonactive.
STATUS	Indicates the administrative state and whether to use the entry. If the status is enabled (default), the entry is used. If the status is disabled, the entry is not used but is saved for future use.

The following table shows the field descriptions for the show ip igmp ssm command.

Table 2. show ip igmp ssm command
Field	Description
DYNAMIC LEARNING	Indicates whether dynamic learning is enabled at a global level.
SSM GROUP RANGE	Indicates the IP address range for the SSM group.