FAQ Week for NLB: Monday

Every day this week the Clustering & High-Availability is writing about some of the top questions we get about Network Load Balancing (NLB) in Windows Server 2008 R2.  We hope you find these helpful!


Gary Jackman

Software Test Engineer

Network Load Balacing




Does NLB require special network adapters?


No, Network Load Balancing can work with any 802.3 network adapter that allows its MAC address to be changed (dynamically updated).  This does include the vast majority of network adapters available today, so almost any 802.3 adapter will work with NLB.  Due to this broad support, it does not even need its own Hardware Compatibility List (HCL)!


One thing to note is that in a virtual environment (such as Hyper-V) there are specific settings on the host server which control the ability to change the MAC address on the VM Guests.  The process to do this is described here: http://blogs.msdn.com/b/clustering/archive/2010/07/01/10033544.aspx.




What is the difference between the “Dedicated IP Address”, “Primary Cluster IP” and “Virtual IP Address”?


The Dedicated IP address (DIP) is the IP address assigned to the NLB network adapter for network traffic not associated with the cluster.  This IP is also used for direct communication with a specific node from other NLB nodes.


The Primary Cluster IP is the first virtual IP address (VIP).  It is the IP address that the NLB cluster’s MAC address is generated from, and is the IP address that is used for the cluster membership heartbeat.


You can have more than one VIP addresses associated with a NLB cluster.  Any other IP address that is not designated as a DIP can be used for communication with the other NLB nodes.