I am creating two NLB clusters (ie 2 seperate farms of servers) and want to use Multicast with IGMP. This works perfectly for the first NLB cluster (given that we have to add the static arp entry for the multicast IGMP mac on the cisco router... 01-00-5e-7f-10-3d). The problem comes when I try to create another NLB cluster using Multicast and IGMP. When I create the second cluster it has the same multicast mac as the first cluster, 01-00-5e-7f-10-3d. Is this default behavior? Is there a way to generate or define a static mac for the second NLB cluster (such as 01-00-5e-7f-10-2d)? Thanks, John KeatingJohn Keating