We have been testing FOG for the past month and multicasting has been the main issue. We also use only Netgear switches (most of them GS748T). Unicast works perfectly fine in our network environment. Multicasting basically brings our network to a halt when trying to multicast only 10 computers. We have tried turn IGMP on with no luck. We have found that only having the computers you want to multicast to connected to the switch, it works fine 4-5 GB/min. Once you add other computers to the switch (ones you are not multicasting to), the speed drops to 30-100MB/min, bringing our network down. After a month of testing we are about through with getting multicasting to work.