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Microsoft KB Archive/102782

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Knowledge Base

Troubleshooting RAS Problems and Using the DEVICE.LOG File

Article ID: 102782

Article Last Modified on 10/31/2006


  • Microsoft Windows NT Advanced Server 3.1
  • Microsoft Windows NT Workstation 3.1
  • Microsoft Windows NT Advanced Server 3.1
  • Microsoft Windows NT Server 3.5
  • Microsoft Windows NT Server 3.51
  • Microsoft Windows NT Workstation 3.5
  • Microsoft Windows NT Workstation 3.51

This article was previously published under Q102782

For information on Windows NT version 4.0, see the following article in the Microsoft Knowledge base:

ARTICLE-ID: 162694
TITLE : How to Capture Modem Commands in Windows NT 4.0

WARNING: Using Registry Editor incorrectly can cause serious, system-wide problems that may require you to reinstall Windows NT to correct them. Microsoft cannot guarantee that any problems resulting from the use of Registry Editor can be solved. Use this tool at your own risk.

If you experience problems connecting to Remote Access Services (RAS), try to identify the specific problem by doing the following:

  1. If you are receiving error messages, choose Help and follow the suggested steps.
  2. Check to see if you can access your modem from the Terminal program. If the modem works with Terminal, do the following:

    a. Make sure your modem is on the list of modems supported by Windows NT Remote Access. (See the Windows NT Hardware Compatibility List.)

    b. Make sure you have the correct cabling required by Remote Access. For more information on RAS cabling requirements, check Remote Access Help. (Search on: Cabling Requirements.)
  3. Enable device logging on Remote Access by doing the following:

    a. Start Registry Editor.

    b. Go to the following subkey:

    hkey_local_machine\system\currentcontrolset \services\rasman\parameters

    c. If the value does not exist, choose Add Value from the Edit menu.

    d. For the following fields, enter these values:

             Value Name: logging<BR/>
             Data Type: REG_DWORD<BR/>
             String: 1

    e. Stop and start Remote Access Service and Phone Book to enable the DEVICE.LOG file.

    The RAS DEVICE.LOG file will be created in the SYSTEM32\RAS subdirectory. See the next section for information on using DEVICE.LOG.


The DEVICE.LOG file contains the strings that are sent to and received from the serial device (either a modem or an X.25 PAD). DEVICE.LOG is useful for troubleshooting problems with serial devices, and for testing new entries added to the MODEM.INF or PAD.INF files.

NOTE: You may want to view the DEVICE.LOG file in a text editor that can display both character and hexadecimal output as some of the information will not be printable characters. Also, DEVICE.LOG contains a carriage return (h0D) and line feed (h0A) byte at the end of each line. These bytes are provided by the program that creates the DEVICE.LOG file and do not represent information communicated from or to the device.

The DEVICE.LOG file contains:

  • The command string sent to the device.
  • The echo of the command.
  • The response from the device.
  • The connect and carrier bps (bits per second) (modems only).

For each bps pair, there may be several sets of command, echo, and response data. If the command and echo (on a modem) do not match, a hardware error message will be generated.

The Connect string from the modem (the last response string from the modem when a connection is established) will normally contain the connect bps, the carrier bps, or both. If the Connect string contains both, the connect bps and the carrier bps lines will give the values from the Connect string. If the Connect string does not have one of the bps values, a best estimate of the actual bps value is given. Both of these values are used by RAS; for this reason, RAS initializes the modem to include both values in its response.

NOTE: "Connect bps" refers to the DTE (data terminal equipment) speed of the modem. This information is required by RAS. The "carrier bps" refers to the DCE (data communication equipment) or modem-to-modem speed. This value is not used internally by RAS, but is displayed if available.

If your modem cannot return both the DTE and DCE speeds, configure it to at least return the DTE speed. Without knowledge of the DTE speed, RAS cannot reset the port appropriately, thus resulting in transmission errors.

Additional query words: prodnt

Keywords: kbnetwork KB102782