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Enumerating Nodes

When you use the standard WMI enumeration procedures to enumerate nodes with the Network Load Balancing (NLB) provider, the results vary as follows:

The following table illustrates enumeration results in a NLB cluster consisting of nodes A, B, C, and D. The results shown for a node are obtained by connecting directly to the node (see Making Direct Connections) and enumerating all available nodes:

Provider node NLB is running Cluster operations are enabled RemoteControlEnabled Enumeration results (in order of appearance)
A
yes
yes
TRUE
A, C
B
yes
yes
FALSE
B, A, C
C
yes
no
TRUE
C, A
D
no
no
TRUE
error
  • Node D does not show up in any enumeration because NLB is not running on that node.
  • Node C shows up in all enumerations even though cluster operations have been stopped on that node.
  • Node B appears only in enumerations performed from node B.
  • WMI allows a connection to Node D, but any provider operation will return an error because NLB is not running on node D.

Because of the behavior described above, WMI enumeration is not a reliable indicator of cluster membership. This is by design. Do not use enumeration as the basis of a NLB cluster membership algorithm. The most accurate method to use to enumerate the nodes in a NLB cluster is to locate the cluster using the cluster IP address. For an example, see Monitoring Application Level Health.