Unicast NLB nodes cannot communicate…

Add a comment April 16th, 2010

One of the most annoying aspects of configuring Microsoft Network Load Balancing on W2K3 in Unicast mode has always been the fact that nodes in a NLB cluster are unable communicate with each other or via each other if you are RDPed into either of them.  Well W2k3 SP2 ended that issue by enabling a simple registry entry that can be added to each node in the cluster that allows them to communicate with each other making administration a bit easier.

1. Click Start, click Run, type regedit, and then click OK.

2. Locate and then click the following registry subkey:
HKLM\System\CurrentControlSet\Services\WLBS\Parameters\Interface\{GUID}
**Note The {GUID} placeholder represents the GUID of the particular NLB instance. You can use the ClusterIPAddress subkey in this hive to identify different NLB clusters.**

3. On the Edit menu, click New, click DWord Value, and then add the following value data. Collapse this tableExpand this tableValue name UnicastInterHostCommSupport, set it’s value to 1.
**Note If you set the UnicastInterHostCommSupport registry entry to any non-zero value, Unicast InterHost Communication Support will be enabled.**

4. Close the Registry Editor.

5. Open a command prompt, and then type the following command:
NLB RELOAD

Read the full KB article at:

http://support.microsoft.com/kb/898867

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