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Q87667: Network Comm. Across Router Using PC-TCP and LAN Manager

Article: Q87667
Product(s): Microsoft LAN Manager
Version(s): 
Operating System(s): 
Keyword(s): 
Last Modified: 30-JUL-2001

SYMPTOMS
========

When FTP Software's PC-TCP stack is used with Microsoft LAN Manager, the network
traffic will not go across a router.

Net Sends, Net Views, and Net Uses to workstations across the router will not
work.

CAUSE
=====

The NetBIOS uses broadcasts for name claims, name resolution, and nondirected
datagrams. The RFCs 1001 and 1002 define three ways in which broadcast traffic
can be handled by a NetBIOS over TCP/IP implementation. These are B-Node
(Broadcast), P-Node (Point-to- Point), and M-Node (Mixed). B-Node uses
broadcasts for name contention and resolution. B-Node broadcasts for name
contention and name resolution do not go through a router. A router will not
allow a broadcast message to pass through to other networks.

FTP Software's implementation of NetBIOS over TCP/IP is purely B-Node based.
Therefore, the B-node broadcasts will not go across a router and network
communications will not take place across the router.

On the other hand, Microsoft's implementation of NetBIOS is also B-node based.
However, the MS TCP/IP stack uses the LMHOSTS file in LAN Manager to provide the
NetBIOS-name-to-IP-address mapping. The LMHOSTS file is located in the
<LANROOT>\ETC directory. By entering the NetBIOS name to IP address
mapping in the LMHOSTS file, the RFC NetBIOS name query request frames for those
names will not be sent to the local network. Instead, the cache containing the
entries in LMHOSTS file will be used to resolve the NetBIOS-name-to-IP-address
mapping. Therefore, broadcasts will not be generated and the machines will be
able to communicate across a router.

RESOLUTION
==========

FTP Software is aware of this situation and according to their technical support
department the new release of the software (version 2.1) will have a feature
similar to Microsoft's implementation. The new release is scheduled to come out
in summer of 1992. For now, the workaround is either to use Microsoft's TCP/IP
stack or to configure the router to bridge the network traffic.

Reference(s):

For more information regarding B-Node, P-Node, and M-Node communications, please
refer to RFCs 1001, 1002, TCP/IP technical notes written by Margaret Johnson, or
the April 1992 issue of "NetNews."

Additional query words:

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Keywords          :  

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