RTP Multicast audio dropouts

Hi All,

I’m making some tests with RTP multicast, sending multicast stream to Barix devices.
There are some dropouts on audio.
Analyzing the Wireshark trace I’ve seen that all the packets are sent two times from Asterisk (duplicated).
Is there a solution?

My system:
FreePBX Distro version: 5.211.65-14 (CentOS 6.5, Kernel 2.6.32-431.el6.i686)
Asterisk version: 11.10.2

From my extension.conf:
exten => 300,1,Dial(MulticastRTP/basic/