How many IGMP versions exist?

There are three versions of the internet Group Management Protocol (IGMP): IGMPv1, IGMPv2, and IGMPv3. IGMPv1, defined in RFC 1112, was the original version, while IGMPv2, introduced in RFC 2236, added features like leave group messages. IGMPv3, specified in RFC 3376, introduced support for source-specific multicast, allowing users to specify which sources they want to receive traffic from. Each version has improved upon the functionality and efficiency of multicast group management.