The Windows system is ultimately in control of the IGMP version used to establish group memberships. Unfortunately there is no socket-level option for our MCast component to set that would control the IGMP version -- it will use whatever the system preference is. For versions of Windows that support multiple versions of IGMP, the preference can be set in the registry. To do so add a DWORD key titled IGMPVersion at Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters to one of the below values:

• 3 for v2
• 4 for v3