For a virtual server to be able to transmit multicast packets, no special configuration is required.
To give a virtual server the ability to receive multicast packets, you must allow it to bind to the multicast address it likes to use. This can be done by creating an interface directory with the selected multicast address in the "ip" file. By creating an empty "nodev" file, no configuration on devices is done when the vserver is started.
/etc/vservers/twonky/interfaces# mkdir 1 /etc/vservers/twonky/interfaces# echo 220.127.116.11 > 1/ip /etc/vservers/twonky/interfaces# touch 1/nodev