JSI Tip 6851. A Windows Server 2003 NLB cluster may not converge when the MTU size is less than the default value?

If you set the MTU size to a value that is less than the default MTU value for your network topology, the heartbeat that is sent by the Network Load Balancing (NLB) server is not properly handled and the cluster may not converge.

The heartbeat protocol does not expect the heartbeats to be fragmented.