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# Cached NetBIOS Names Can Affect TCP Session Establishment

PSS ID Number: Q120820

Article Last Modified on 11-10-1999

The information in this article applies to:

- Microsoft LAN Manager 2.2b

## Symptoms

When a server initializes, it registers a unique NetBIOS name. When a client attempts to connect to the server it obtains the server's NetBIOS Name and the IP address by broadcasting a NAME QUERY frame and receiving a Name Query Response Frame.
The client maintains a name cache table, which associates NetBIOS names with corresponding IP addresses. If a server happens to go off line, and another server with a different IP address registers the same NetBIOS Name then the clients may not be able to connect to the new server.

## Cause

The name cache table on the LAN Manager client machines is not updated. Attempts to establish a new session may fail because TCP uses the old (incorrect) IP address that exists in the cache.

## Workaround

In the VxD version of the TCP/IP stack for Windows for Workgroups 3.11, the name cache can be controlled through the CacheTimeout entry. Setting this value very low resolves this problem under WFWG 3.11. Modify the following entry in SYSTEM.INI:

       [NBT] section
       CacheTimeout=60000
       (The value is in millisecs, 60000ms = 1 minute.
       The default: is 360000 millisecs or 6 Minutes.)

The only workaround on a LAN Manager client is to reboot the client. It should also be noted this problem occurs only with TCP/IP transport.

## Status

Microsoft has confirmed this to be a problem in LAN Manager version 2.2b. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

Additional query words: wfw wfwg 2.20b tcp

Keywords:
Issue Type:
Technology: kbAudDeveloper kbLanManSearch kbLanMan220b