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Changing the IGMP Version

By default, the router runs IGMPv2. Routers running different versions of IGMP negotiate the lowest common version of IGMP that is supported by hosts on their subnet and operate in that version.

To enable SSM functionality, you must configure version 3 on the host and the host’s directly connected router. If a source address is specified in a multicast group that is statically configured, the version must be set to IGMPv3.

Note: If a static multicast group is configured with the source address defined and the IGMP version is configured to be version 2, the source is ignored and only the group is added. In this case the join is treated as an IGMPv2 group join.

To change to IGMPv3 (for source-specific multicast [SSM] functionality), include the version statement:

version 3;

You can include this statement at the following hierarchy levels:

If you configure the IGMP version setting at the individual interface hierarchy level it overrides configuring the IGMP version using the interface statement and specifying the all option.

Note: If you have already configured the router to use IGMP version 1 (IGMPv1) and then configure it to use IGMPv2, the router continues to use IGMPv1 for up to 6 minutes and then uses IGMPv2.


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