Using Network Registrar with Windows NT/Windows 95

The following information applies if you are running Network Registrar on a Windows NT or Windows 95 system:

To ensure that the server processes get their share of the CPU, set the Windows NT scheduler so that it shares the processor equally among all the processes. If you fail to do this, it might lead to various timeouts. This setting is located under System in the Control Panel. On Windows NT 3.51, select Tasking, and set the foreground and background performance to Equally Responsive. On Windows NT 4.0, select the Performance tab and set the foreground performance boost to None.
To avoid filling up the Windows NT event log, make sure that you change the Log Settings to Overwrite Events as Needed. For instructions on how to change the event log settings, refer to your Windows NT documentation.

Caution If you fail to change your log settings your DNS and/or DHCP servers may stop responding if the logs get full.

In Windows NT 3.51 Service Pack 5, Microsoft has introduced a bug in the Windows NT Performance Monitor, perfmon.exe. If the pathname of a dll that perfmon needs to open is too long (about 70 characters seems to be the limit), the Performance Monitor fails. The Windows NT Performance Monitor may exit or display the following message:

The instruction at 0x referenced memory at 0x

: The only work-around is either to put dlls in directories that are not too deeply nested, or to revert to a previous version of the Performance Monitor. The versions from Service Pack 2 and earlier appear to work correctly.

Vendor-Specific DHCP Client Information

This section contains information that relates to specific DHCP clients and their operation with the Network Registrar DHCP server.

Microsoft Clients for Windows 95 and Windows NT 3.51

When Microsoft DHCP clients renew their leases, they do not recognize changes in the values of options that they have requested. When a Microsoft client first obtains a lease, it requests options for DNS servers, WINS servers, network gateways, etc. If an administrator later changes one or more of these options' values, the server sends the new values when clients renew their leases. These Microsoft clients do not recognize that these values have changed, and will not update the values that they are using.

To cause the client to use the updated option values, force the client to release and reacquire a lease. On Windows 95 use winipcfg.exe. On Windows NT use ipconfig /release then ipconfig/renew in order to release and require the client's IP address. You can also reboot the client PC.

Windows 95

The DHCP client included in the Windows 95 system works well with the Network Registrar DHCP server, but be aware of the issues described in the following sections.

Difficulty Acquiring a Lease

The Windows 95 DHCP client has a two-second timeout for the time between when it accepts an offer of a IP address in a message sent to the server, and the time it expects an acknowledgment of that acceptance from the server in reply. (In comparison, Windows NT has a four-second timeout.)

In the rare event that this timeout is not sufficient, you will see the following message on the Windows 95 machine:

Unable to obtain an IP network address.

This relatively short timeout is not generally a problem and you will not usually experience difficulties, but in the following situations the potential for problems is increased:

When the Windows 95 DHCP client and the Network Registrar DHCP server are separated by one or more routers, the packet travel time and the time the server takes to respond could cause the Windows 95 DHCP client to fail to obtain an IP address.
If you have been instructed by Technical Support to enable debug logging for the Network Registrar DHCP server, the amount of time spent logging may slow down the DHCP server. If the server's ability to respond was already close to the two-second limit (perhaps because of routers between the DHCP client and the Network Registrar DHCP server), then the debug logging could slow the server just enough to trigger this problem.
You can obtain a patch from Microsoft to change the timeout on Windows 95 from two seconds to the four seconds used on Windows NT. The patch was created 2/12/96, and includes a file called Vdhcp.386. The patch itself is called VDHCPUPD.EXE.

Difficulty Using a Lease After Expiration

Two situations have occurred where a Windows 95 machine experienced a system error condition that caused it to fail to renew a lease on an IP address. Long after the lease expired, the machine responded to ARP requests for the IP address that it was previously authorized to use. This was significant because the IP address to which it was incorrectly responding was legitimately offered to a second Windows 95 machine. When this second machine tried to ARP for that address to confirm that the address was unused, the failing machine responded to the ARP request. The second machine reported that the address was already in use (as did the failing machine). This situation could have been prevented by enabling PING and recording the MAC address of the offending machine.

To recover from this situation:

Step 1 On the machine that was offered the lease and determines that it was already in use (which will usually be the machine of the individual who first noticed this problem), examine the error box and record both the IP address and the MAC address of the machine that is listed as causing the conflict.

Step 2 Reboot the second machine (the one that was offered the address that was still being used erroneously).

The machine should obtain a new address, and work correctly from then on.

Step 3 Determine which machine was causing this conflict and reboot it.

Determining which machine caused this conflict might be difficult. If your clients have set up host names on their machines (whether or not you are using Dynamic DNS update), you can use the log files for the DHCP server to help you locate the host name of the machine that caused this problem. To do this, use the MAC address recorded in step one and search through the log files to see if you can determine when that machine got its IP address. You can also search for the IP address in the log. If you find the IP address and MAC address, you can determine the host name of the machine and perhaps that will help you locate the hung machine.

Step 4 Clear the deactivated status of the lease address in question.

Failure to Acquire a Lease After Expiration

Several situations have occurred where Windows 95 machines let a lease expire, and then try and fail to reacquire a lease. The machines were in the INIT state (where they were doing a DHCP DISCOVER), and multiple DHCP servers were offering leases, but the Windows 95 machine failed to accept any of the offers. The Windows client did apparently not see the offers, but this could not be verified. This has happened with both the Network Registrar DHCP server as well as the Windows NT 3.51 DHCP server.

To recover from this problem, reboot the affected Windows 95 machine. You can also clear this problem by shutting down the Ethernet interface on the Windows 95 machine and reinitializing it, although this is a more time-consuming and error-prone solution.

Network Driver Exceptions

Microsoft has recently confirmed that a bug in the Windows 95 DHCP client software may cause an error in the NDIS driver or in the MAC driver. A system that experiences this failure displays a blue screen with a brief message containing the names of the drivers where the error occurred. Sometimes you can simply press a key and continue operating after seeing this error message. This problem only occurs on laptop computers using PCMCIA card network interfaces, although the description of the bug does not exclude desktop computers. Some PCMCIA card RJ45 adapters (dongles) seem to be disconnect-prone. This exception can be provoked sometimes by moving a laptop's adapter so that the link or connectivity is lost while using winipcfg.exe to release and renew the laptop's lease. For more information, see the knowledge-base article Q158713 on the Microsoft website at:

http://support.microsoft.com/support/kb/articles/q158/7/13.asp.

Token Ring OE Errors

A number of fatal exception OE errors can occur when booting token ring Windows 95 clients. Microsoft Knowledge Base article Q158713 confirms this as a Windows 95 bug that occurs most frequently with token ring cards, but sometimes with Ethernet cards. For more information, see:

http://support.microsoft.com/support/kb/articles/q158/7/13.asp.

Table of Contents

Using Network Registrar with Windows NT/Windows 95