Nokia’s routers are capable of interoperating with routers and hosts running IGMPv1, IGMPv2, and, or IGMPv3. RFC 5186, Internet Group Management Protocol Version 3 (IGMPv3)/Multicast Listener Discovery Version 2 (MLDv2) and Multicast Routing Protocol Interaction explores some of the interoperability issues and how they affect the various routing protocols.
IGMP version 3 specifies that if at any point a router receives an older version query message on an interface that it must immediately switch into a compatibility mode with that earlier version. Because none of the previous versions of IGMP are source aware, should this occur and the interface switch to Version 1 or 2 compatibility mode, any previously learned group memberships with specific sources (learned via the IGMPv3 specific INCLUDE or EXCLUDE mechanisms) must be converted to non-source specific group memberships. The routing protocol then treats this as if there is no EXCLUDE definition present.