Cannot use Wlbs.exe remote control commands from load balanced VPN servers

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This article was previously published under Q269004

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SYMPTOMS

If you use the Wlbs.exe command line to remotely control a Network Load Balancing (NLB) cluster node that is part of an NLB cluster that is load balancing Point-to-Point Tunneling Protocol (PPTP) services, you may receive the following error message:

C:\wlbs query 192.168.0.1
WLBS Cluster Control Utility V2.3. (c) 1997-99 Microsoft Corporation
Accessing cluster '192.168.0.1' (192.168.0.1):
Did not receive response from the cluster.

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CAUSE

This behavior can occur if you use the wizard to configure the node as a Virtual Private Network (VPN) server. If Routing and Remote Access (RRAS) is enabled, the wizard creates specific filters that block all TCP/UDP traffic (other than for the filtered ports PPTP, L2TP, and IPSEC). The filters prevent remote control operations which use UDP port 2504.

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RESOLUTION

The command-line interface (Wlbs.exe) or Windows Management Instrumentation (WMI) provider can be used to control WLBS NLB operations either:

Locally from each node

-or-
Remotely from a server/workstation that is not part of the cluster.

To work around this issue, copy the Wlbs.exe file to the computer, and then run the commands. This workaround is successful because the WLBS driver sits below TCP/IP, and the call on UDP Port 2504 is intercepted before reaching TCP/IP, where the filtering would be applied.

More information about this issue is available in the "Windows 2000 Network Load Balancing Technical Overview" white paper that can be found at the following Microsoft Web site:

http://technet.microsoft.com/en-us/library/bb742455.aspx (http://technet.microsoft.com/en-us/library/bb742455.aspx)

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