When ISA Server Can’t Set Up NLB Parameters

ISA Server services use Windows Management Instrumentation ( WMI) to control Network Load Balancing (NLB) parameters. It may happen that the compiled version of NLB Managed Object Format (MOF) files gets corrupted or incorrectly registered so that ISA Server is not able to control NLB anymore.

In this case:


· ISA Server is going to report a catastrophic failure alert for the NLB node (the array member) where NLB failed to be controlled by ISA Server.

· Looking at Network adapter properties will show that no NLB settings have been configured and even NLB is disabled for that NIC.

· “Network Load Balancing Manager” tool is going to report an error for failing NLB nodes.

Remark: This may happen only on some ISA Server nodes participating in the NLB cluster, leaving the ISA Server array partially working. That is, the nodes that are able to join the NLB cluster will work, and the others will be treated as "down" by NLB.

To solve this issue follow these steps on the failing server:

  1. Reboot the server in safe mode.
  2. In a command prompt, type NET STOP WINMGMT
  3. Move contents of %windir%\system32\wbem\repository to a temp folder
  4. In the command prompt, type NET START WINMGMT
  5. Reboot the server in normal mode
  6. Go to the command prompt %windir%\system32\webm> and type the following entries:

· mofcomp.exe cimwin32.mof

· mofcomp wlbsprov.mof

· mofcomp nlbmprov.mof

  1. Reboot the server and check that the node is recognized by NLB.

Franck Heilmann

Escalation Engineer EMEA ISA team