Hosts in a Network Load Balancing (NLB) cluster are configured to load balance network traffic. Host configuration is set by using NLB Manager, and if it is not configured properly, the NLB cluster may not function correctly.
Check that the cluster IGMP multicast address is valid
If the Network Load Balancing (NLB) cluster detects that the Internet Group Management Protocol (IGMP) multicast IP address is invalid, you should check the NLB configuration and make sure that the cluster IGMP multicast IP address is in a valid format.
To check the IGMP address:
Click Start, click Administrative Tools, and then click Network Load Balancing Manager. You can also open NLB Manager by typing Nlbmgr at a command prompt.
If NLB Manager does not already list the cluster, connect to the cluster.
Right-click the cluster, and then click Cluster Properties.
Ensure that the IGMP multicast check box is selected to enable IGMP support on all hosts in the cluster. When you enable IGMP support, the allowed multicast IP address is restricted to the standard class D range; that is, 188.8.131.52 to 184.108.40.206.