If routers run different versions of MLD, they negotiates the lowest common version of MLD that is supported on their subnet and operate in that version.
Version 1
Specified in RFC 2710, Multicast Listener Discovery (MLD) for IPv6, was the first deployed version and included low leave latency, that is, a reduction in the time it takes for a multicast router to learn that there are no longer any members of a group present on an attached network.
Version 2
Specified in RFC 3810, Multicast Listener Discovery Version 2 (MLDv2) for IPv6, adds support for source filtering, that is, the ability for a system to report interest in receiving packets only from specific source addresses, as required to support Source-Specific Multicast.
Multicast (SSM)), or from all but specific source addresses, sent to a multicast address. MLDv2 must keep state per group per attached network. This group state consists of a filter mode, a list of sources, and various timers. For each attached network running MLD, a multicast router records the wanted reception state for that network.