This article describes the issue of Multicast not passing Iperf testing.
Multicast does not pass Iperf testing.
To test PIM functionality, the receiver needs to send an IGMP Join. If the tool being used does not send an IGMP Join, the PIM register sessions will fail. With Iperf, the server side (receiver) does not form an IGMP join. So, the Multicast PIM register will fail. The recommended testing tools are the Microsoft based Wsend and Wlisten tools. You can download them from the following link: http://www.microsoft.com/en-us/download/details.aspx?id=17657