I have a 10.7 server with deploy studio and multi casting works fine while imaging. I got a new 10.11 mac mini server and installed deploy studio and multi cast wont work for me. Same Vlan, same settings. Not sure what might cause this. The client boots up but as when they go to start the imaging it stops and then says multicast failed. I check the logs and it says could not join multi cast stream. Unicast works fine and again it works fine on the 10.7 server even using the same network cable and switch and port.