Currently , IGMP v1, v2 is supported from the user guide of netx-duo.
IGMP Configuration Options
NX_DISABLE_IGMP_INFO Defined, disables IGMP information gathering.
NX_DISABLE_IGMPV2 Defined, disables IGMPv2 support, and NetX Duo supports
IGMPv1 only. By default this option is not set and is defined
What about IGMP v3 ?
No information provided in the release, So assume in current release V3 is not supported.