I finally had time to work this all out, and the answer was pretty easy.  I actually had the right approach some time ago, but unfortunately was guided away from it. In any case the solution was as follows: 1. Change the NLB cluster type to Multicast with IGMP 2. For all switches, globally turn Bridge Filtering On, and IGMP Snooping On 3. Ensure that Bridge Multicast Forwarding Mode is set to Forward Unregistered on all switches 4. Create a new Bridge Multicast group on each switch.  For the switchs which host the NLB, make the LAG ports members of the multicast group.  For all other switches, make all uplink ports which connect to the destination switch members. This tells all of the switches how to direct this particular multicast traffic.  Prior to getting this setup, clients would broadcast out web requests to the proxy NLB IP which would flood the request traffic across all switch ports on all switches.  Now the traffic is directed only to uplink ports, and the actual LAG ports of the NLB cluster members. Hopefully this will help someone in the future. Troy.
Some time ago I configured a Network Load Balacing (NLB) cluster to serve web traffic in our organization.  Shortly thereafter I realized that my change to using NLB meant that web traffic was being broadcast throughout the domain!  I have a fairly basic knowledge of switches and such, and so I'm hoping to get some assistence in configuring my system to prevent this multicast flooding. First let me share a picture which outlines the small section of my network in question. Both switches are PowerConnect 6248s, joined by a single copper port.  On VMHOST1 I have Hyper-V virtual machine running third party web proxy software, which is configured in a multicast NLB with a virtual machine running the same software on VMHOST2.  The VMHOST servers each connect to their respective switches with a four port LAG group, and of course there is some complexity with a software based virtual switch on each HOST server which is part of the Hyper-V configuration. [IMAGE]   The NLB is configured in multicast mode, however IGMP is not currently enabled.  This NLB configuration was specified by the third party web proxy that I am using in the NLB.  I have opened a case with them to understand why they want IGMP turned off.  If my VERY limited understanding is correct, and I can turn on IGMP support for my NLB then I should be able to do some configuration on the switches to better handle the muticast traffic. Sadly I'm unclear on what needs to be done at the switch level to make this happen.  I believe it's some combination of IGMP Snooping, Bridge Multicast Grouping, and maybe some filters but I could really use some help and guidance here to get the specifics. Thanks a million!      
Trying to limit switch flooding from a Microsoft Windows Network Load Balacing 
(NLB)