Either the Windows NT Loading Balancing Service or the Network Load Balancing Computer Is Unable to Log on to the Network (283963)

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Transmission Control Protocol/Internet Protocol (TCP/IP) cannot distinguish between the different adapters on the same subnet. This behavior means that the computer can send out packets from the Network Load Balancing adapter to talk to a domain controller on the same subnet. If this behavior occurs on a 2-node WLBS or Network Load Balancing configuration, there is a 50 percent chance that this computer is the computer that discards the packets coming back from the domain controller.

When the packets are received individually, they are not discarded and each individual computer works correctly. When the packets are received with either WLBS or Network Load Balancing disabled, the computers also work (because the packets have not been discarded).

When you attempt to trace the source of the behavior, you may determine that the WLBS or the Network Load Balancing virtual adapter is the source IP, and that the responses are from the domain controller (going to the WLBS or the Network Load Balancing adapter). The responses actually reach the client computer, and then are discarded.

If you isolate the WLBS or the Network Load Balancing cluster to its own subnet, you can work around this behavior because the default gateway (that has been set up only for the dedicated network adapter) can force all packets to go through the dedicated network adapter.