We recently enhanced our network with switched Ethernet technology. All the servers and workstations in the network run Windows NT 4.0 with the latest service pack. Although this enhancement provided a faster network, it presented a problem that hadn't previously occurred.

When booted, some of the faster workstations in the network (Pentium III processor—class systems) reported a Netlogon error (event ID 5719—No Windows NT Domain Controller is available for domain) in the System event log. Sometimes, if the user logged off and logged on again without restarting the computer, all services would start without problems. None of the slower computers produced this error message.

After trying workarounds such as upgrading the NIC software, I hadn't found a solution. Finally, I came across the Microsoft article "Increase Domain Logon Timeout over Network" (http://support.microsoft.com/support/kb/articles/q163/2/04.asp), which provided a solution: Use a registry editor to add the ExpectedDialupDelay parameter of type REG_DWORD to the HKEY_LOCAL_MACHINE\SYSTEM\ CurrentControlSet\Services\Netlogon\Parameters subkey. This value has a range of 0 to 600 seconds. To find the right timeout value, I experimented a bit and came up with a value for my network of from 4 to 8 seconds. My theory is that this logon delay is necessary to let the switches build entries in their routing tables as soon as the client starts.