You are the network administrator for your company. The network consists of a single Active Directory domain. All computers on the network are members of the domain. You administer a four-node Network Load Balancing cluster. All nodes run Windows Server 2003. The cluster has converged successfully.

You use Network Load Balancing Manager on the default host to configure all nodes of the cluster. The nodes have a single network adapter and are connected to the same switching hub device. Administrators of non-cluster servers that are connected to the same switching hub device report that their servers receive traffic that is destined for the cluster nodes. Receiving this additional network traffic impairs the network performance of the non-cluster servers.

You need to ensure that traffic destined for only the cluster nodes is not sent to all ports of the switching hub device. You do not want to move the cluster to another switching hub device.

What should you do?

A.
On each node, run the wlbs.exe drainstop command.

B.
On one node, run the nlb.exe reload command.

C.
Use Network Load Balancing Manager to enable Internet Group Management Protocol (IGMP) support on the cluster.

D.
Use Network Load Balancing Manager to add a second cluster IP address.

Explanation:
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If you enable IGMP Multicast, NLB attempts to prevent switch flooding by limiting multicast traffic to only those ports on a switch that have a NLB-bound network adapter connected to them. So, when you use IGMP Multicast, traffic is designed to flow only to those switch ports connected to NLB cluster hosts, thus preventing all other switch ports from being flooded by the multicast traffic.

Reference:

Craig Zacker, MCSE Self-Paced Training Kit (Exam 70-293): Planning and Maintaining a Microsoft Windows Server 2003 Network Infrastructure, Microsoft Press, Redmond, Washington, 2004, p. 7: