If routers run different versions of IGMP, they negotiate the lowest common version of IGMP that is supported on their subnet and operate in that version. Three versions of IGMP are supported:
Version 1
Specified in RFC 1112, Host extensions for IP Multicasting was the first widely deployed version and the first version to become an Internet standard.
Version 2
Specified in RFC 2236, Internet Group Management Protocol added support for ‟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 particular group present on an attached network.
Version 3
Specified in RFC 3376, Internet Group Management Protocol added 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 SSM, or from all but specific source addresses, sent to a particular multicast address.
IGMPv3 must keep track of the state of each group for each attached network. The group state consists of a filter-mode, a list of sources, and various timers. For each attached network running IGMP, a multicast router records the desired reception state for that network.