Multicast data traffic flows down the source tree to active forwarding vPC peer device. vPC peer device 1 (7K1) sends a copy of the multicast traffic out of the vPC member port connected to access switch. One another copy is sent out of vPC peer-link. As there is no single-attached device (or orphan port) interested by this multicast traffic on the other side, vPC peer device 2 (7K2) will drop the multicast traffic.