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							<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Npcap Users' Guide</title><meta name="generator" content="DocBook XSL Stylesheets V1.79.2"><meta name="description" content="The Users' Guide covers the basics of installing and removing Npcap, interactions with WinPcap, frequently asked questions, and how to report bugs."><link rel="home" href="index.html" title="Npcap Reference Guide"><link rel="up" href="index.html" title="Npcap Reference Guide"><link rel="prev" href="index.html" title="Npcap Reference Guide"><link rel="next" href="npcap-devguide.html" title="Developing software with Npcap"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Npcap Users' Guide</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="index.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="npcap-devguide.html">Next</a></td></tr></table><hr></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="npcap-users-guide"></a>Npcap Users' Guide</h2></div><div><div class="abstract"><p class="title"><b>Abstract</b></p>
      <p>The Users' Guide covers the basics of installing and removing
        Npcap, interactions with WinPcap, frequently asked questions,
        and how to report bugs.</p>
    </div></div></div></div>
  
  

  <p>Because Npcap is a packet capture architecture, not merely a software
    library, some aspects of installation and configuration may fall to the end
    user. This Users' Guide covers the basics of installing, configuring, and
    removing Npcap, as well as how to report bugs.</p>

  <div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="npcap-installation"></a>Installation</h3></div></div></div>
    

    <p>
      Npcap is distributed as a signed executable installer, downloadable from
      <a class="ulink" href="https://npcap.com/#download" target="_top">Nmap.com</a>. Major
      versions are backwards-compatible, and users of the free non-commercial
      version are encouraged to upgrade regularly for security and stability
      fixes. Software distributors may have separate requirements for supported
      Npcap versions.  Please refer to
      <a class="ulink" href="https://npcap.com/#license" target="_top">the Npcap License</a> for
      terms of use and redistribution.</p>

    <p>
      The Npcap installer and uninstaller are easy to use in
      <span class="quote">&#8220;<span class="quote">Graphical Mode</span>&#8221;</span> (direct run) and <span class="quote">&#8220;<span class="quote">Silent Mode</span>&#8221;</span> (run with
      <code class="option">/S</code> parameter, available only with <a class="ulink" href="https://npcap.com/oem/" target="_top">Npcap OEM</a>).
    </p>

    <div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a name="npcap-installation-options"></a>Installer options</h4></div></div></div>
      
      <p>
        The installer accepts several command-line options that correspond to the
        options presented in the graphical interface (GUI).  The options can be
        set by command-line flags taking the form
        <code class="option">/<em class="replaceable"><code>name</code></em>=<em class="replaceable"><code>value</code></em></code>.
      </p>
      <p>The values for these options must be one of:
      </p>
      <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><code class="option">yes</code>: select the option</p></li><li class="listitem"><p><code class="option">no</code>: unselect the option</p></li><li class="listitem"><p><code class="option">enforced</code>: select the option and make it unchangable in the GUI</p></li><li class="listitem"><p><code class="option">disabled</code>: unselect the option and make it unchangable in the GUI</p></li></ul></div>
      <div class="sect4"><div class="titlepage"><div><div><h5 class="title"><a name="npcap-installer-options-gui"></a>Graphical installer options</h5></div></div></div>
        
        <p>The following options are presented as checkboxes in the
          installer, but can be set or locked via command-line flags. Unless
          otherwise noted, the default for these options is <code class="option">no</code>.
        </p>

        <div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">/loopback_support</code></span></dt><dd><p>
		<span class="emphasis"><em>Legacy loopback support for Nmap 7.80 and older. Not needed for Wireshark.</em></span>
		Older versions of Npcap required a Microsoft KM-TEST loopback
		adapter to be installed in order to capture and inject loopback
		traffic. This is no longer needed, but some software won't be
		able to do loopback injection unless the adapter is installed.
		Use this option to install the legacy loopback adapter if
		needed.
              </p>
              <p>See <a class="xref" href="npcap-devguide.html#npcap-feature-loopback" title="For software that uses Npcap loopback feature">the section called &#8220;For software that uses Npcap loopback feature&#8221;</a> for more
                information.
            </p></dd><dt><span class="term"><code class="option">/admin_only</code></span></dt><dd><p>
                <span class="emphasis"><em>Restrict Npcap driver's access to Administrators
                  only</em></span>. When this option is chosen, the devices
                created by the Npcap driver for capture and injection on each
                network adapter will be created with a restrictive ACL that
                only allows access to the device by the SYSTEM and built-in
                Administrators. Because this level of access requires UAC
                elevation, a helper binary, <code class="literal">NpcapHelper.exe</code>,
                is used to request elevation for each process that opens a
                capture handle.
            </p></dd><dt><span class="term"><code class="option">/dot11_support</code></span></dt><dd><p>
                <span class="emphasis"><em>Support raw 802.11 traffic (and monitor mode) for
                  wireless adapters</em></span>. This option installs a second
                Lightweight Filter Driver that uses the Native WiFi API to
                capture raw 802.11 WiFi frames on devices that are put into
                network monitor mode. Captured frames are given a Radiotap
                header. Not all hardware or network drivers support the Native
                WiFi API.
            </p></dd><dt><span class="term"><code class="option">/winpcap_mode</code></span></dt><dd><p>
                <span class="emphasis"><em>Install Npcap in WinPcap API-compatible
                  Mode</em></span>. The default for this option is
		  <code class="option">yes</code> in Npcap 0.9985 and later. Npcap's DLLs
                    have always been installed into a separate
                    <code class="literal">Npcap</code> subdirectory of the system
                    directory to avoid conflicting with existing WinPcap
                    installations. This option also installs the DLLs to the
                    system directory, replacing WinPcap. Any existing WinPcap
                    installation will be removed.
              </p>
              <p>
            </p></dd><dt><span class="term"><code class="option">/prior_driver</code></span></dt><dd><p>
		<span class="emphasis"><em>Install older driver</em></span>.  Microsoft continues to tighten their policy on what
		types of certificates and authorities may sign drivers. In cases where the current driver may
		not strictly meet these requirements, the <code class="option">/prior_driver</code> option may be used to
		install the last version of the driver that meets these requirements.  In cases where no such
		driver exists, this option is ignored.
              </p>
              <p>
            </p></dd></dl></div>
      </div>

      <div class="sect4"><div class="titlepage"><div><div><h5 class="title"><a name="npcap-installer-options-cli"></a>Command-line installation options</h5></div></div></div>
        
        <p>Some advanced or deprecated options are only available on the
          command-line. Options marked <code class="literal">(deprecated)</code> are
          subject to removal in future versions.</p>

        <div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">/S</code> (Silent install, Npcap OEM only)</span></dt><dd><p>
                Installs Npcap without showing any graphical windows or
                prompts. This option is case-sensitive. Silent install is available only for Npcap OEM.
            </p></dd><dt><span class="term"><code class="option">/disable_restore_point</code></span></dt><dd><p>
                The default for this option is <code class="option">yes</code>, so the
                installer will not set a system restore point.  Windows may
                independently create a restore point because of the driver
                installation independent from this option. To ensure a
                restore point is made, specify
                <code class="option">/disable_restore_point=no</code>.
            </p></dd><dt><span class="term"><code class="option">/no_kill</code></span></dt><dd><p>
                Control termination of
                processes using Npcap during upgrades or WinPcap when
                <code class="option">/winpcap_mode=yes</code> is chosen. See
                <a class="xref" href="npcap-users-guide.html#npcap-installation-uninstall-options" title="Uninstaller options">the section called &#8220;Uninstaller options&#8221;</a>
                for more detailed discussion.
            </p></dd><dt><span class="term"><code class="option">/require_version</code></span></dt><dd><p>
		Uninstall and replace an existing Npcap installation even if it
		is newer than this version of the installer. By default, the
		Npcap installer will not remove and replace a version of Npcap
		that is newer than its own. In GUI mode, this hides the message
		box asking the user how to proceed.
            </p></dd><dt><span class="term"><code class="option">/require_features</code></span></dt><dd><p>
		Uninstall and replace an existing Npcap installation of any
		version if it does not provide the same features as the other
		command-line options specify. Features are the /winpcap_mode,
		/dot11_support, /loopback_support, and /admin_only options.
            </p></dd><dt><span class="term"><code class="option">/force</code></span></dt><dd><p>
		Uninstall and replace an existing Npcap installation regardless
		of version or whether the installation would be modified. By
		default, the Npcap installer will not remove and replace a
		Npcap installation of the same version unless the install
		options would be modified. In GUI mode, this hides the message
		box asking the user how to proceed.
            </p></dd><dt><span class="term"><code class="option">/D</code> (destination directory)</span></dt><dd><p>
                The destination directory for installation can be overridden by
                the <code class="option">/D</code> option, with a few restrictions. First, it will
                only affect where Npcap keeps its installation logs and helper utilities.
                The driver and DLLs will always be installed into the appropriate
                directories below <span class="command"><strong>%SYSTEMROOT%\System32\</strong></span>. Second, the
                <code class="option">/D</code> must be the last option in the command, and the path
                must not contain quotes. This option is case-sensitive. For example, to change the installation directory
                to <code class="filename">C:\Path With Spaces\</code>, the invocation would be:
                <span class="command"><strong>npcap-<em class="replaceable"><code>version</code></em>.exe /D=C:\Path With Spaces</strong></span>
            </p></dd><dt><span class="term"><code class="option">/npf_startup</code> (deprecated)</span></dt><dd><p>
                <span class="emphasis"><em>Automatically start the Npcap driver at boot
                  time</em></span>. This option defaults to
                <code class="option">yes</code>, because Windows expects NDIS filter
                drivers to be available at boot time. If you choose to disable
                this, Windows may not start networking for up to 90 seconds
                after boot.
            </p></dd><dt><span class="term"><code class="option">/vlan_support</code> (deprecated, ignored)</span></dt><dd><p>
                <span class="emphasis"><em>Support 802.1Q VLAN tag when capturing and sending
                  data (currently unsupported)</em></span>. This feature was
                disabled in 2016 to prevent a crash and has not been
                re-enabled.
            </p></dd></dl></div>

      </div>
    </div>

    <div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a name="npcap-installation-uninstall-options"></a>Uninstaller options</h4></div></div></div>
      
      <p>
        The uninstaller provided with Npcap also accepts some command-line options.
      </p>
      <div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">/S</code> (Silent uninstall)</span></dt><dd>
            <p>Uninstalls Npcap without showing any graphical windows or
              prompts. Silent uninstall is available in all editions of Npcap,
              not just Npcap OEM. If Npcap OEM installer in silent mode needs
              to uninstall an older Npcap installation, it passes the
              <code class="option">/S</code> option to the existing uninstaller. This option is case-sensitive.</p>
          </dd><dt><span class="term"><code class="option">/Q</code> (Quick uninstall)</span></dt><dd>
            <p>Skips the confirmation page and finish page in the uninstall
            wizard. This option does not have any meaning for silent
            uninstalls.</p>
          </dd><dt><span class="term"><code class="option">/no_kill</code>=<em class="replaceable"><code>yes|no</code></em> (do not kill processes)</span></dt><dd>
            <p>Controls how the uninstaller handles processes that are still using
              Npcap at the time of uninstall. The default value is
              <code class="literal">no</code>, which allows the uninstaller to terminate
              processes that would block Npcap from being uninstalled. If
              <code class="option">/no_kill=yes</code> is specified, then Npcap
              uninstaller will fail if there are still applications using Npcap
              driver or DLLs.</p>

            <p>In the default case, <code class="option">/no_kill=no</code>, the
              graphical uninstaller will give the user the choice to manually
              close the offending programs, have the uninstaller terminate
              them, or abort the uninstallation.  In silent mode, Npcap
              uninstaller will immediately terminate any command-line processes
              that are using Npcap (like a Nmap process that is still
              scanning), and wait for at most 15 seconds to gracefully
              terminate any GUI processes that are using Npcap (like Wireshark
              UI that is still capturing).  <span class="quote">&#8220;<span class="quote">Gracefully</span>&#8221;</span> means
              that if you are still capturing via Wireshark, Wireshark UI will
              prompt the user about whether to save the current capture before
              closing. The user will have 15 seconds to save his session.
              <span class="emphasis"><em>Note:</em></span> although Npcap uninstaller won't
              terminate Wireshark UI processes immediately, the live capture
              stops immediately. This is because Wireshark UI uses command-line
              processes named <code class="varname">dumpcap.exe</code> to capture, and
              that command-line process will be terminated immediately.</p>

            <p>If this option is provided on the
              <span class="emphasis"><em>installer</em></span> command line, it will be passed to
              the Npcap uninstaller when doing an upgrade or
              replacement.</p>
          </dd></dl></div>

    </div>

    <div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a name="npcap-installation-options-disabled"></a>Disabled and enforced options for GUI Mode</h4></div></div></div>
      

      <p>
        We may disable or enforce certain options in the installer GUI to make them unselectable. This
        usually means that those options can easily cause compatibility issues and are considered
        not suitable for most users, or we think we need to enforce some rules for the Npcap API. Advanced users can still change their states via command-line
        parameters, which is described in following sections.
      </p>

      <p>
        Fortunately, if a distributor wants to start the Npcap installer GUI and disable or enforce
        certain options for reasons like compatibility. It can also use the four value
        mechanism by setting the command-line parameters to <code class="option">disabled</code> or <code class="option">enforced</code>.
        For example, the following command will start an installer GUI with the
        <code class="option">loopback_support</code> option disabled and unselected:
      </p>

      <p>
        <span class="command"><strong>npcap-<em class="replaceable"><code>version</code></em>.exe /loopback_support=disabled</strong></span>
      </p>
    </div>

  </div>

  <div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="npcap-platforms"></a>Windows platforms supported</h3></div></div></div>
	  
	  <p>Npcap supports all Windows versions currently supported by Microsoft. Depending on Windows version, the
		  driver may support a different NDIS version, which corresponds to a set of network stack
		  features.</p>
	  <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
			  <p>On <span class="emphasis"><em>Windows 10</em></span>, <span class="emphasis"><em>Windows Server 2016</em></span>, and
				  <span class="emphasis"><em>Windows Server 2019</em></span>, Npcap installs a NDIS 6.50
				  driver.</p></li><li class="listitem">
			  <p>On <span class="emphasis"><em>Windows 8.1</em></span>, <span class="emphasis"><em>Windows 8</em></span>,
				  <span class="emphasis"><em>Windows Server 2012 R2</em></span>, and
				  <span class="emphasis"><em>Windows Server 2012</em></span>,
				  Npcap installs a NDIS 6.30 driver.</p></li><li class="listitem">
			  <p>On <span class="emphasis"><em>Windows 7</em></span> and <span class="emphasis"><em>Windows Server 2008 R2</em></span>, Npcap
				  installs a NDIS 6.20 driver.</p></li></ul></div>
	  <p>Microsoft will end Extended support for Windows versions prior to Windows 10 on January 10, 2023. After
		  that time, new Npcap releases <span class="emphasis"><em>may</em></span> omit support for these operating
		  systems.</p>
	  <p>Npcap can be installed on x86, x86-64, and ARM64. DLLs for the native architecture will be installed, as
		  well as x86 DLLs for applications running in 32-bit emulation.</p>
  </div>

  <div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="npcap-feature-dot11-wireshark"></a>How to use Wireshark to capture raw 802.11 traffic in <span class="quote">&#8220;<span class="quote">Monitor Mode</span>&#8221;</span></h3></div></div></div>
    

    <p>
      The latest Wireshark has already integrated the support for Npcap's <span class="quote">&#8220;<span class="quote">Monitor Mode</span>&#8221;</span> capture.
      If you want to use Wireshark to capture raw 802.11 traffic in <span class="quote">&#8220;<span class="quote">Monitor Mode</span>&#8221;</span>, you need to
      switch on the monitor mode inside the Wireshark UI instead of using <a class="xref" href="npcap-devguide.html#npcap-feature-dot11-wlanhelper" title="WlanHelper">the section called &#8220;WlanHelper&#8221;</a>.
      This is because Wireshark only recognizes the monitor mode set by itself. So when you turn
      on monitor mode outside Wireshark (like in <code class="filename">WlanHelper</code>), Wireshark will not know the adapter
      has been in monitor mode, and will still try to capture in Ethernet mode, which will get no traffic.

      So after all, the correct steps are:
    </p>

    <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Install latest version Wireshark and latest version Npcap with
          <code class="option">Support raw 802.11 traffic</code> option checked.</p></li><li class="listitem"><p>Launch Wireshark QT UI (GTK version is similar), go to <span class="quote">&#8220;<span class="quote">Capture options</span>&#8221;</span>.
          Then toggle the checkbox in the <span class="quote">&#8220;<span class="quote">Monitor Mode</span>&#8221;</span> column of your wireless adapter's row.
          Click the <span class="quote">&#8220;<span class="quote">Start</span>&#8221;</span> button. If you see a horizontal line instead of the checkbox,
          then it probably means that your adapter doesn't support monitor mode. You can use the
          <code class="filename">WlanHelper</code> tool to double-check this fact.</p></li><li class="listitem"><p>To decrypt <span class="emphasis"><em>encrypted 802.11 data</em></span>
          packets, you need to specify the decipher key in Wireshark, otherwise
          you will only see 802.11 data packets.</p></li><li class="listitem"><p>Stop the capture in Wireshark UI when you finishes capturing, the monitor mode
          will be turned off automatically by Npcap.</p></li></ul></div>
  </div>

  <div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="npcap-qa"></a>Q &amp; A</h3></div></div></div>
    

    <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Network interruption while installing Npcap: Installing a filter driver may
	    cause brief interruptions to network connectivity based on the specific changes needed
	    to install the driver in the network stack. This known issue is documented as
	    <a class="ulink" href="" target="_top">issue #53</a> on our tracker.</p>
	<p> A separate issue is a longer interruption in connectivity if the
	    <code class="varname">npcap</code> service is not started, which used to be an installer option.
	    As Microsoft states <a class="ulink" href="https://support.microsoft.com/en-us/kb/2019184" target="_top">here</a>,
          <span class="emphasis"><em>an optional NDIS light-weight filter (LWF) driver like Npcap could cause
            90-second delay in network availability</em></span>. Some solutions you could try
          are: 1) wait for 90 seconds; 2) disable and re-enable the adapter icon in
          <span class="command"><strong>ncpa.cpl</strong></span>; 3) reboot. If the network is still unable to connect,
          please <a class="ulink" href="http://issues.npcap.org/new?title=Npcap+Bug+Report" target="_top">file a bug report</a>.
      </p></li><li class="listitem"><p>Installation fails with error code <code class="varname">0x8004a029</code>:
          The cause is that you have <span class="quote">&#8220;<span class="quote">reached the maximum number of network filter
            drivers</span>&#8221;</span>, see solution
          <a class="ulink" href="https://social.technet.microsoft.com/Forums/windows/en-US/4deb27fc-33ce-4fc0-a26f-3fec5b57733d/is-there-a-maximum-number-of-network-filter-drivers-in-windows-7?forum=w7itpronetworking" target="_top">here</a>.
      </p></li><li class="listitem"><p>Npcap Loopback Adapter is missing (legacy loopback support):
          The legacy Npcap Loopback Adapter is actually a wrapper of Microsoft Loopback Adapter.
          Such adapters won't show up in Wireshark if the <code class="varname">Basic Filtering Enging (BFE)</code>
          service was not running. To fix this issue, you should start this service at <code class="varname">services.msc</code>
          manually and restart the Npcap service by running <span class="command"><strong>net stop npcap</strong></span>
          and <span class="command"><strong>net start npcap</strong></span>. See details about this issue
          <a class="ulink" href="https://github.com/nmap/nmap/issues/802" target="_top">here</a>.
      </p></li><li class="listitem"><p>Npcap only captures TCP handshake and teardown, but not data packets.
          Some network adapters support offloading of tasks to free up CPU time for
          performance reasons. When this happens, Npcap may not receive all of the
          packets, or may receive them in a different form than is actually sent on the
          wire. To avoid this issue, you may disable TCP Chimney, IP Checksum
          Offloading, and Large Send Offloading in the network adapter properites on
          Windows. See details about this issue in
          <a class="ulink" href="https://github.com/nmap/nmap/issues/989" target="_top">issue
            #989</a> on our tracker.
      </p></li></ul></div>
  </div>

  <div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="npcap-issues"></a>Reporting Bugs</h3></div></div></div>
    

    <p>
      Please report any bugs or issues about Npcap on
      <a class="ulink" href="http://issues.npcap.org/new?title=Npcap+Bug+Report" target="_top">the Nmap Project's Issues tracker</a>.
      In your report, please provide your <span class="emphasis"><em>DiagReport</em></span> output, user
      software version (e.g. Nmap, Wireshark), steps to reproduce the problem, and other information
      you think necessary. If your issue occurs only on a particular OS version (e.g. Win10
      1511, 1607), please mention it in the report.
    </p>

    <div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a name="npcap-issues-diagreport"></a>Diagnostic report</h4></div></div></div>
      

      <p>
        Npcap has provided a diagnostic utility called <code class="filename">DiagReport</code>.
        It provides a lot of information including OS metadata, Npcap related files,
        install options, registry values, services, etc. You can simply click the
        <code class="filename">C:\Program Files\Npcap\DiagReport.bat</code> file to run <code class="filename">DiagReport</code>.
        It will pop up a text report via Notepad (it's stored in: <code class="filename">C:\Program Files\Npcap\DiagReport.txt</code>).
        Please always submit it to us if you encounter any issues.
      </p>

    </div>
    <div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a name="npcap-issues-installation-log"></a>General installation log</h4></div></div></div>
      

      <p>
        Npcap keeps track of the installation in a log file:
        <code class="filename">C:\Program Files\Npcap\install.log</code>. Please submit it
        together in your report if you encounter issues during the installation
        (e.g. the installer halts).
      </p>
    </div>

    <div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a name="npcap-issues-driver-installation-log"></a>Driver installation log</h4></div></div></div>
      

      <p>
        Npcap keeps track of the driver installation (aka commands run by
        <code class="filename">NPFInstall.exe</code>) in a log file:
        <code class="filename">C:\Program Files\Npcap\NPFInstall.log</code>, please submit
        it together in your report if you encounter issues during the driver
        installation or problems with the <span class="quote">&#8220;<span class="quote">Npcap Loopback Adapter</span>&#8221;</span>.
      </p>

      <p>
        There's another system-provided driver installation log in:
        <code class="filename">C:\Windows\INF\setupapi.dev.log</code>.
        If you encounter errors during the driver/service installation, please copy
        the Npcap-related lines out and send them together in
        your report.
      </p>
    </div>

    <div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a name="npcap-issues-packet-log"></a>Dynamic link library (DLL) log</h4></div></div></div>
      

      <p>
        For problems with Npcap's regular operation, you may need to obtain a
        debug log from <code class="filename">Packet.dll</code>.  To do this, you will
        need a debug build of Npcap.  If you are a Npcap developer, you can build
        the <code class="filename">Packet.sln</code> project with the
        <code class="varname">_DEBUG_TO_FILE</code> macro defined. If you are an end user,
        you can contact the Npcap development team for the latest Npcap debug
        build.  The debugging process will continue to append to the debug log
        (<code class="filename">C:\Program Files\Npcap\Packet.log</code>), so you may want
        to delete it after an amount of time, or save your output to another
        place before it gets too large.
      </p>
    </div>

    <div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a name="npcap-issues-driver-log"></a>Driver log</h4></div></div></div>
      

      <p>
        If there is an issue with the Npcap driver, you can open an
        <span class="emphasis"><em>Administrator</em></span> command prompt,  enter <span class="command"><strong>sc query
          npcap</strong></span> to query the driver status and <span class="command"><strong>net start
          npcap</strong></span> to start the driver (replace
        <em class="replaceable"><code>npcap</code></em> with <em class="replaceable"><code>npf</code></em> if you
        installed Npcap in <span class="quote">&#8220;<span class="quote">WinPcap Compatible Mode</span>&#8221;</span>).  The command
        output will inform you whether there's an error. If the driver is running
        well, but the issue still exists, then you may need to check the driver's
        log. Normal Npcap releases don't switch on the driver log function for
        performance. Contact the Npcap development team to obtain a driver-debug
        version of the Npcap installer.  When you have got an appropriate
        driver-debug version Npcap, you need to use <a class="ulink" href="https://technet.microsoft.com/en-us/sysinternals/debugview.aspx" target="_top">DbgView</a>
        to read the Windows kernel log (which contains our driver log).  You may
        need to turn on DbgView before installing Npcap, if the error occurs when
        the driver loads. When done, save the DbgView output to a file and submit
        it in your report.
      </p>
    </div>
    <div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a name="npcap-issues-bsod"></a>Blue screen of death (BSoD) dump</h4></div></div></div>
      

      <p>
        If you encountered BSoD when using Npcap, please attach the minidump
        file (in <code class="filename">C:\Windows\Minidump\</code>) to your report
        together with the Npcap version. We may ask you to provide the full
        dump (<code class="filename">C:\Windows\MEMORY.DMP</code>) for further troubleshooting.
      </p>
    </div>
  </div>

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