A lot of people have asked about setting up NLB clusters on virtual machines. This is possible. But, there a few things to keep in mind.
If you’re trying to create NLB clusters using Virtual Server Virtual Machines, before designing your solution familiarize yourself with the supported configurations. Refer to http://support.microsoft.com/kb/925476 for details on which configurations are supported.
If you’re trying to create NLB clusters using Hyper-V Virtual Machines with Windows Server 2008 RTM (not R2) host(s), there are a few things to be aware of (more details at http://support.microsoft.com/kb/953828):
1- Apply the fix in the KB article to each of the Windows Server 2008 VM guests that are cluster nodes. Note that this fix will be included in Windows Server 2008 SP2.
2- NLB changes the MAC address of the machine when you bind NLB on a node, change the operation mode of the cluster, change the primary IP of the cluster, or unbind NLB from the node. Hyper-V in Windows Server 2008 requires a reboot of the VM if its MAC address is changed. The KB article describes the process to follow to create a new cluster or add nodes to a cluster using Hyper-V VMs.
If you’re trying to create NLB clusters using Hyper-V Virtual Machines with Windows Server 2008 R2 host(s), there a few things to be aware of:
1- Enable MAC spoofing for the virtual network used by NLB in the guests. This can be done from the Network Adapter settings on each VM that is participating in a cluster as a node. You can create NLB clusters, add nodes, and update NLB cluster configurations without having to reboot the VMs at all.
2- If the VM guest is Windows Server 2008 (not R2) and it is an NLB cluster node, you will need to apply the fix at http://support.microsoft.com/kb/953828 (or use SP2). This is not applicable if your guest is Windows Server 2008 R2 or Windows Server 2008 SP2 (you do not need to apply the fix).
3- When you apply SP2 to the VM guest running Windows Server 2008, make sure you upgrade the integration services for that VM. This can be done by connecting to the VM, selecting Action from the menu, selecting “Insert Integration Services Setup Disk”, and then following the steps in the VM.
Senior Program Manager
Clustering & High-Availability