Hello All :
In complement of this :
https://wiki.fogproject.org/wiki/index.php/FOG_security
I put here my multicast rules for iptables (implemented into my separate node )
iptables -A -s 224.0.0.0/4 -j ACCEPT
iptables -A FORWARD -s 224.0.0.0/4 -d 224.0.0.0/4 -j ACCEPT
iptables -A OUTPUT -d 224.0.0.0/4 -j ACCEPT