Multihomed Primary Domain Controller Causes Browsing Problems

ID: Q244983

The information in this article applies to:
  • Microsoft Windows NT Server version 4.0

SYMPTOMS

When you use a multihomed primary domain controller (PDC), you may experience browsing problems and NetBIOS name resolution errors.


CAUSE

This issue can occur because each browser service bound to each interface operates independently. The PDC maintains a separate cumulative list on each interface, but the lists are not merged. A master browser that exchanges lists with the PDC on one interface does not obtain a list of servers discovered by a master browser that is exchanging lists with the PDC on the other interface. Because the browser service does not merge the browse list for separate networks, the PDC should not be multihomed.


RESOLUTION

To resolve this issue, unbind the WINS Client (TCP/IP) protocol from the second adapter:

NOTE: After unbinding the additional adapters, verify that the WINS database and any LMHosts files do not refer to the Internet Protocol (IP) address of the unbound adapters. WINS may need to be purged to register the old entries for the second network interface card (NIC) out of the WINS database.

  1. Click Start, point to Settings, click Control Panel, and then double-click Network.


  2. Click Bindings.


  3. In the Show Bindings For box, click All Protocols.


  4. Double-click the WINS Client (TCP/IP) protocol branch to expand the list of adapters bound to the protocol.


  5. To disable the network binding between the WINS Client (TCP/IP) protocol and the second network adapter, click the second network adapter, and click Disable.


  6. Click OK, and then click Close.


  7. Click Yes to restart your computer.



MORE INFORMATION

When browsing does not work on a multihomed computer, the transport that did not work can be identified in Event Viewer by locating text similar to this: 'The browser was unable to retrieve a list of servers from the browser master primary domain controller name on the network \device name\transport name' or 'The browser service has failed to retrieve the backup list too many times on transport of transport name'. The transport for NetBIOS over TCP/IP appears as 'NetBT_network card driver name', such as 'NetBT_E100B1'. The transport for other protocols appears as:

NetBEUI protocol appears as: Nbf_network card name.

IPX/SPX protocol appears as: NwlnkIpx (the network card name does not appear).

NetBIOS over NwLink appears as: NwLnkNB (the network card name does not appear).
Microsoft Windows NT version 4.0 introduced the 'UnboundBindings' setting, and this can be used to prevent the PDC from directly gathering a browse list on more than one interface. However, this setting does not force the master browsers in the domain to use only the bound interface card. If WINS is used to provide the IP address for the master browser to find the PDC, there is no way of guaranteeing that the correct interface is chosen. This limitation cannot be overcome with Windows NT 4.0. To guarantee that it can merge a single, domain-wide list, the PDC must not be a multihomed computer.

The following procedure describes how to edit the registry to enable the UnboundBindings parameter, which will prevent the PDC from directly gathering a browse list on more than one interface. In versions of Windows NT Server earlier than version 4.0, it was not possible to browse across subnets that were connected by a PDC server configured with TCP/IP routing and WINS. In NT 4.0, the parameter UnboundBindings can be added to the registry of the multihomed domain master browser to disable the binding between the second NIC and the browser service. On a multihomed PDC running WINS, all WINS entries should have the IP address of the one network adapter that has the browser service enabled.

IMPORTANT: This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. For information about how to do this, view the "Restoring the Registry" Help topic in Regedit.exe or the "Restoring a Registry Key" Help topic in Regedt32.exe.


WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys and Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it. If you are running Windows NT, you should also update your Emergency Repair Disk (ERD).


  1. Use Registry Editor to locate the following key in the registry:


    2. 
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Browser\Parameters
  2. Add a REG_MULTI_SZ value named UnboundBindings with a value of NetBT_network adapter name to this key, where network adapter name is the name of the network adapter on which to disable the binding to the browser service.

    NOTE: You can determine the names of your network cards by typing NET CONFIG RDR at the command prompt. The network cards are indicated by NetBT_NIC type, where NIC type is the type of network interface card on your computer. You can also find the names of your network adapters in the following registry key: 
    
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services
    Each network adapter has multiple entries in the registry. A network card entry that ends in a number contains the settings for a specific instance of the card. Select the instance of the card where you want to disable the bindings to the browser service.

    For example, for a computer with two Intel EtherExpress Pro 100B network adapters, there are three registry keys, 'E100B' and 'E100B1' and 'E100B2', in HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services. The first entry, 'E100B', contains the driver and binding information for all the Intel EtherExpress Pro 100B cards. The entry 'E100B1' contains the settings for the first instance of the card. The settings for the second instance of the card is listed in the registry as 'E100B2'. To disable the bindings to the browser on the second network card, type NetBT_E100B2 in the String text box.

    If there are more than two network adapters on the multihomed PDC computer, type on a separate line of the String field the name of each network adapter to disable the browser bindings.


  3. Restart the computer to enable the new settings.


  4. After the computer restarts, look in the Event Log to make sure the new settings are working properly:


    1. Start Event Viewer.


    2. Inspect the System event log for one occurrence of the following event that corresponds to the adapter on which the binding to the browser service is enabled:


      3. Source: Browser
      Event: 8015 (The browser has forced an election on network device because a Windows NT Server (or domain master) browser is started.)
For additional information regarding multihomed Windows NT 4.0 computers, please see the following articles in the Microsoft Knowledge Base:
Q181774 Multihomed Issues with Windows NT
Q221210 Browsing with a Multihomed PDC
Q158487 Browsing Across Subnets w/ a Multihomed PDC in Windows NT 4.0
Q191611 Symptoms of Multihomed Browsers

Additional query words: nt 4.0 domain controller multiple nic

Keywords : nt 4.0
Version : winnt:4.0
Platform : winnt
Issue type : kbprb


Last Reviewed: November 9, 1999
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