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Q276446: Branch Servers Using DLS Use Dynamic Port for SnaBase Connection

Article: Q276446
Product(s): Microsoft SNA Server
Version(s): 3.0 (all SP),4.0,4.0 SP1,4.0 SP2,4.0 SP3
Operating System(s): 
Keyword(s): kbsna300sp1 kbsna300sp2 kbsna300sp3 kbsna300sp4 sna4 kbsna400sp1 kbsna400sp2 kbsna400sp
Last Modified: 12-JUN-2001

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The information in this article applies to:

- Microsoft SNA Server, versions 3.0 SP1, 3.0 SP2, 3.0 SP3, 3.0 SP4, 4.0, 4.0 SP1, 4.0 SP2, 4.0 SP3 
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SUMMARY
=======

Branch-based SNA Servers that use a Remote Link Service may not be able to
communicate with a central SNA Server if Internet firewalls or screening routers
between the SNA Server systems are filtering outgoing Transfer Control
Protocol/Internet Protocol (TCP/IP) ports in addition to incoming TCP/IP ports.

Branch-based SNA Servers open a connection to a central SNA Server's SnaBase
service in order to initialize the distributed host connection. The TCP/IP
source port that is used by the branch server for this SnaBase connection is
dynamic. If there is a firewall or screening router between the branch and
central SNA Server that is filtering on outgoing ports, the firewall will not
forward the responses from the central SNA Server to the branch SNA Server
because the "dynamic" source port will not be known to the firewall.

NOTE: In most cases that involve firewalls (or screening routers), only the
incoming TCP/IP ports are filtered, so this would not be an issue. The filtering
of outgoing TCP/IP ports is not as common as filtering incoming ports.

For additional information about the latest service pack for SNA Server 4.0,
click the article number below to view the article in the Microsoft Knowledge
Base:

  Q215838 How to Obtain the Latest SNA Server Version 4.0 Service Pack

MORE INFORMATION
================

The following Knowledge Base articles describe how to configure SNA Servers to
use specific (static) TCP/IP ports and ranges of ports when using Distributed
Link Services (DLS) in environments that use firewalls and/or screening routers:
For additional information, click the article numbers below to view the articles
in the Microsoft Knowledge Base:

  Q164590 Branch Servers Using DLS Cannot Communicate Through Firewalls

  Q224303 SNA Server Allows Range of IP Ports with Distributed Link Service

After you apply the update, the branch-based SNA Servers that use the methods
described by the referenced articles will also use static TCP/IP ports (or a
range of static ports) to open connections to a central SNA Server's SnaBase
service.

NOTE: A range of ports should be used for the reasons described in the referenced
articles.



Additional query words: Snaip sp1 sp2 sp3

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Keywords          : kbsna300sp1 kbsna300sp2 kbsna300sp3 kbsna300sp4 sna4 kbsna400sp1 kbsna400sp2 kbsna400sp3 
Technology        : kbAudDeveloper kbSNAServSearch kbSNAServ400 kbSNAServ300SP3 kbSNAServ300SP1 kbSNAServ400SP1 kbSNAServ400SP2 kbSNAServ400SP3 kbSNAServ300SP2 kbSNAServ300SP4
Version           : :3.0 (all SP),4.0,4.0 SP1,4.0 SP2,4.0 SP3
Issue type        : kbinfo

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