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Q101878: Windows NT RAS Server Port Reset

Article: Q101878
Product(s): Microsoft Windows NT
Version(s): 3.1 4.0
Operating System(s): 
Keyword(s): kbnetwork
Last Modified: 08-AUG-2001

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The information in this article applies to:

- Microsoft Windows NT Advanced Server, version 3.1 
- Microsoft Windows NT Server version 4.0 
- Microsoft Windows NT Workstation version 4.0 
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SUMMARY
=======

Windows NT Remote Access Server attempts to reset its serial ports when it
detects that the phone line has been hung up. The server detects a disconnect
when either Data Carrier Detect (DCD) or Data Set Ready (DSR) signals are
dropped by the server's modem. After a few seconds, the server sends an
initialization string to the modem, putting the modem in auto-answer mode, and
configures the modem options. In Windows NT 4.0, the initialization string is
pulled from the particular manufacturer's Mdm*.inf file. In Windows NT versions
prior to NT 4.0, the initialization string is pulled from the Modem.inf file for
the particular modem type.

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

Data Carrier Detect (DCD)
-------------------------

Pin 8 on a DB 25 serial connector. This line is set high by the server modem when
it is receiving a carrier signal from the remote modem. The carrier signal is a
tone at a specific frequency that, by itself, does not carry any information.
Information is actually conveyed by changes in the carrier signal's amplitude,
frequency, phase, or some combination. When a phone line is disconnected, the
carrier tone is interrupted. This causes the DCD signal to be dropped.

Data Set Ready (DSR)
--------------------

Pin 6 on a DB 25 serial connector. When this signal is high, it indicates that
the modem is powered on and is ready to receive commands.

Troubleshooting
---------------

If you hang up your Remote Access Server (RAS) client and your RAS server modem
does not reset to receive a new call, you may be having troubles with DSR or
DCD. On the server, look at the port status in the RAS Admin application. If the
port status says "Connected, user authenticated" even though the modem is
disconnected, this indicates a problem. Check your serial cable wiring with the
RAS requirements found in the online help files. If the modem is not wired
properly, the DCD or DSR signals may not be received by the server.

Some modems allow you to override DSR and DCD with dip switches and modem
commands. Make sure these signals are allowed to function normally. These
problems sometimes show themselves as the server not resetting the port until
the AUTODISCONNECT timer expires. The line disconnects but the server does not
detect it. The server leaves the line open, waiting for more data. However, more
data never arrives. After the server waits for AUTODISCONNECT time (20 minutes
is the default), it drops the line and sends the initialization strings that
will reset the modem.

Additional query words: prodnt NTRAS

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Keywords          : kbnetwork 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400 kbWinNTAdvSerSearch kbWinNTAdvServ310 kbWinNT310Search
Version           : 3.1 4.0

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