Microsoft NLB weirdness

NLB (Network Load Balancing) is a clustering tech. used by Microsoft products. There are two NLB methods:

• Unicast NLB
• Multicast NLB

NLB is a software clustering tech. and should be avoided. You are better off using Hardware load balancers such as Citrix Netscaler.

NLB has a bad design and using it causes switch flooding. The reason to this is it's ARP/MAC address usage.

To avoid problems where NLB must be used, check configuration examples for Cisco Devices. Catalyst Switches for Microsoft Network Load Balancing Configuration Example