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  1. <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>
    2. 

  2.       <p>The Users' Guide covers the basics of installing and removing
    3. 

  3.         Npcap, interactions with WinPcap, frequently asked questions,
    4. 

  4.         and how to report bugs.</p>
    5. 

  5.     </div></div></div></div>
    6. 

  6.   
    7. 

  7.   
    8. 

  8. 

  9.   <p>Because Npcap is a packet capture architecture, not merely a software
    10. 

  10.     library, some aspects of installation and configuration may fall to the end
    11. 

  11.     user. This Users' Guide covers the basics of installing, configuring, and
    12. 

  12.     removing Npcap, as well as how to report bugs.</p>
    13. 

  13. 

  14.   <div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="npcap-installation"></a>Installation</h3></div></div></div>
    15. 

  15.     
    16. 

  16. 

  17.     <p>
    18. 

  18.       Npcap is distributed as a signed executable installer, downloadable from
    19. 

  19.       <a class="ulink" href="https://npcap.com/#download" target="_top">Nmap.com</a>. Major
    20. 

  20.       versions are backwards-compatible, and users of the free non-commercial
    21. 

  21.       version are encouraged to upgrade regularly for security and stability
    22. 

  22.       fixes. Software distributors may have separate requirements for supported
    23. 

  23.       Npcap versions.  Please refer to
    24. 

  24.       <a class="ulink" href="https://npcap.com/#license" target="_top">the Npcap License</a> for
    25. 

  25.       terms of use and redistribution.</p>
    26. 

  26. 

  27.     <p>
    28. 

  28.       The Npcap installer and uninstaller are easy to use in
    29. 

  29.       <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
    30. 

  30.       <code class="option">/S</code> parameter, available only with <a class="ulink" href="https://npcap.com/oem/" target="_top">Npcap OEM</a>).
    31. 

  31.     </p>
    32. 

  32. 

  33.     <div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a name="npcap-installation-options"></a>Installer options</h4></div></div></div>
    34. 

  34.       
    35. 

  35.       <p>
    36. 

  36.         The installer accepts several command-line options that correspond to the
    37. 

  37.         options presented in the graphical interface (GUI).  The options can be
    38. 

  38.         set by command-line flags taking the form
    39. 

  39.         <code class="option">/<em class="replaceable"><code>name</code></em>=<em class="replaceable"><code>value</code></em></code>.
    40. 

  40.       </p>
    41. 

  41.       <p>The values for these options must be one of:
    42. 

  42.       </p>
    43. 

  43.       <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>
    44. 

  44.       <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>
    45. 

  45.         
    46. 

  46.         <p>The following options are presented as checkboxes in the
    47. 

  47.           installer, but can be set or locked via command-line flags. Unless
    48. 

  48.           otherwise noted, the default for these options is <code class="option">no</code>.
    49. 

  49.         </p>
    50. 

  50. 

  51.         <div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">/loopback_support</code></span></dt><dd><p>
    52. 

  52. 		<span class="emphasis"><em>Legacy loopback support for Nmap 7.80 and older. Not needed for Wireshark.</em></span>
    53. 

  53. 		Older versions of Npcap required a Microsoft KM-TEST loopback
    54. 

  54. 		adapter to be installed in order to capture and inject loopback
    55. 

  55. 		traffic. This is no longer needed, but some software won't be
    56. 

  56. 		able to do loopback injection unless the adapter is installed.
    57. 

  57. 		Use this option to install the legacy loopback adapter if
    58. 

  58. 		needed.
    59. 

  59.               </p>
    60. 

  60.               <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
    61. 

  61.                 information.
    62. 

  62.             </p></dd><dt><span class="term"><code class="option">/admin_only</code></span></dt><dd><p>
    63. 

  63.                 <span class="emphasis"><em>Restrict Npcap driver's access to Administrators
    64. 

  64.                   only</em></span>. When this option is chosen, the devices
    65. 

  65.                 created by the Npcap driver for capture and injection on each
    66. 

  66.                 network adapter will be created with a restrictive ACL that
    67. 

  67.                 only allows access to the device by the SYSTEM and built-in
    68. 

  68.                 Administrators. Because this level of access requires UAC
    69. 

  69.                 elevation, a helper binary, <code class="literal">NpcapHelper.exe</code>,
    70. 

  70.                 is used to request elevation for each process that opens a
    71. 

  71.                 capture handle.
    72. 

  72.             </p></dd><dt><span class="term"><code class="option">/dot11_support</code></span></dt><dd><p>
    73. 

  73.                 <span class="emphasis"><em>Support raw 802.11 traffic (and monitor mode) for
    74. 

  74.                   wireless adapters</em></span>. This option installs a second
    75. 

  75.                 Lightweight Filter Driver that uses the Native WiFi API to
    76. 

  76.                 capture raw 802.11 WiFi frames on devices that are put into
    77. 

  77.                 network monitor mode. Captured frames are given a Radiotap
    78. 

  78.                 header. Not all hardware or network drivers support the Native
    79. 

  79.                 WiFi API.
    80. 

  80.             </p></dd><dt><span class="term"><code class="option">/winpcap_mode</code></span></dt><dd><p>
    81. 

  81.                 <span class="emphasis"><em>Install Npcap in WinPcap API-compatible
    82. 

  82.                   Mode</em></span>. The default for this option is
    83. 

  83. 		  <code class="option">yes</code> in Npcap 0.9985 and later. Npcap's DLLs
    84. 

  84.                     have always been installed into a separate
    85. 

  85.                     <code class="literal">Npcap</code> subdirectory of the system
    86. 

  86.                     directory to avoid conflicting with existing WinPcap
    87. 

  87.                     installations. This option also installs the DLLs to the
    88. 

  88.                     system directory, replacing WinPcap. Any existing WinPcap
    89. 

  89.                     installation will be removed.
    90. 

  90.               </p>
    91. 

  91.               <p>
    92. 

  92.             </p></dd><dt><span class="term"><code class="option">/prior_driver</code></span></dt><dd><p>
    93. 

  93. 		<span class="emphasis"><em>Install older driver</em></span>.  Microsoft continues to tighten their policy on what
    94. 

  94. 		types of certificates and authorities may sign drivers. In cases where the current driver may
    95. 

  95. 		not strictly meet these requirements, the <code class="option">/prior_driver</code> option may be used to
    96. 

  96. 		install the last version of the driver that meets these requirements.  In cases where no such
    97. 

  97. 		driver exists, this option is ignored.
    98. 

  98.               </p>
    99. 

  99.               <p>
    100. 

  100.             </p></dd></dl></div>
    101. 

  101.       </div>
    102. 

  102. 

  103.       <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>
    104. 

  104.         
    105. 

  105.         <p>Some advanced or deprecated options are only available on the
    106. 

  106.           command-line. Options marked <code class="literal">(deprecated)</code> are
    107. 

  107.           subject to removal in future versions.</p>
    108. 

  108. 

  109.         <div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">/S</code> (Silent install, Npcap OEM only)</span></dt><dd><p>
    110. 

  110.                 Installs Npcap without showing any graphical windows or
    111. 

  111.                 prompts. This option is case-sensitive. Silent install is available only for Npcap OEM.
    112. 

  112.             </p></dd><dt><span class="term"><code class="option">/disable_restore_point</code></span></dt><dd><p>
    113. 

  113.                 The default for this option is <code class="option">yes</code>, so the
    114. 

  114.                 installer will not set a system restore point.  Windows may
    115. 

  115.                 independently create a restore point because of the driver
    116. 

  116.                 installation independent from this option. To ensure a
    117. 

  117.                 restore point is made, specify
    118. 

  118.                 <code class="option">/disable_restore_point=no</code>.
    119. 

  119.             </p></dd><dt><span class="term"><code class="option">/no_kill</code></span></dt><dd><p>
    120. 

  120.                 Control termination of
    121. 

  121.                 processes using Npcap during upgrades or WinPcap when
    122. 

  122.                 <code class="option">/winpcap_mode=yes</code> is chosen. See
    123. 

  123.                 <a class="xref" href="npcap-users-guide.html#npcap-installation-uninstall-options" title="Uninstaller options">the section called &#8220;Uninstaller options&#8221;</a>
    124. 

  124.                 for more detailed discussion.
    125. 

  125.             </p></dd><dt><span class="term"><code class="option">/require_version</code></span></dt><dd><p>
    126. 

  126. 		Uninstall and replace an existing Npcap installation even if it
    127. 

  127. 		is newer than this version of the installer. By default, the
    128. 

  128. 		Npcap installer will not remove and replace a version of Npcap
    129. 

  129. 		that is newer than its own. In GUI mode, this hides the message
    130. 

  130. 		box asking the user how to proceed.
    131. 

  131.             </p></dd><dt><span class="term"><code class="option">/require_features</code></span></dt><dd><p>
    132. 

  132. 		Uninstall and replace an existing Npcap installation of any
    133. 

  133. 		version if it does not provide the same features as the other
    134. 

  134. 		command-line options specify. Features are the /winpcap_mode,
    135. 

  135. 		/dot11_support, /loopback_support, and /admin_only options.
    136. 

  136.             </p></dd><dt><span class="term"><code class="option">/force</code></span></dt><dd><p>
    137. 

  137. 		Uninstall and replace an existing Npcap installation regardless
    138. 

  138. 		of version or whether the installation would be modified. By
    139. 

  139. 		default, the Npcap installer will not remove and replace a
    140. 

  140. 		Npcap installation of the same version unless the install
    141. 

  141. 		options would be modified. In GUI mode, this hides the message
    142. 

  142. 		box asking the user how to proceed.
    143. 

  143.             </p></dd><dt><span class="term"><code class="option">/D</code> (destination directory)</span></dt><dd><p>
    144. 

  144.                 The destination directory for installation can be overridden by
    145. 

  145.                 the <code class="option">/D</code> option, with a few restrictions. First, it will
    146. 

  146.                 only affect where Npcap keeps its installation logs and helper utilities.
    147. 

  147.                 The driver and DLLs will always be installed into the appropriate
    148. 

  148.                 directories below <span class="command"><strong>%SYSTEMROOT%\System32\</strong></span>. Second, the
    149. 

  149.                 <code class="option">/D</code> must be the last option in the command, and the path
    150. 

  150.                 must not contain quotes. This option is case-sensitive. For example, to change the installation directory
    151. 

  151.                 to <code class="filename">C:\Path With Spaces\</code>, the invocation would be:
    152. 

  152.                 <span class="command"><strong>npcap-<em class="replaceable"><code>version</code></em>.exe /D=C:\Path With Spaces</strong></span>
    153. 

  153.             </p></dd><dt><span class="term"><code class="option">/npf_startup</code> (deprecated)</span></dt><dd><p>
    154. 

  154.                 <span class="emphasis"><em>Automatically start the Npcap driver at boot
    155. 

  155.                   time</em></span>. This option defaults to
    156. 

  156.                 <code class="option">yes</code>, because Windows expects NDIS filter
    157. 

  157.                 drivers to be available at boot time. If you choose to disable
    158. 

  158.                 this, Windows may not start networking for up to 90 seconds
    159. 

  159.                 after boot.
    160. 

  160.             </p></dd><dt><span class="term"><code class="option">/vlan_support</code> (deprecated, ignored)</span></dt><dd><p>
    161. 

  161.                 <span class="emphasis"><em>Support 802.1Q VLAN tag when capturing and sending
    162. 

  162.                   data (currently unsupported)</em></span>. This feature was
    163. 

  163.                 disabled in 2016 to prevent a crash and has not been
    164. 

  164.                 re-enabled.
    165. 

  165.             </p></dd></dl></div>
    166. 

  166. 

  167.       </div>
    168. 

  168.     </div>
    169. 

  169. 

  170.     <div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a name="npcap-installation-uninstall-options"></a>Uninstaller options</h4></div></div></div>
    171. 

  171.       
    172. 

  172.       <p>
    173. 

  173.         The uninstaller provided with Npcap also accepts some command-line options.
    174. 

  174.       </p>
    175. 

  175.       <div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">/S</code> (Silent uninstall)</span></dt><dd>
    176. 

  176.             <p>Uninstalls Npcap without showing any graphical windows or
    177. 

  177.               prompts. Silent uninstall is available in all editions of Npcap,
    178. 

  178.               not just Npcap OEM. If Npcap OEM installer in silent mode needs
    179. 

  179.               to uninstall an older Npcap installation, it passes the
    180. 

  180.               <code class="option">/S</code> option to the existing uninstaller. This option is case-sensitive.</p>
    181. 

  181.           </dd><dt><span class="term"><code class="option">/Q</code> (Quick uninstall)</span></dt><dd>
    182. 

  182.             <p>Skips the confirmation page and finish page in the uninstall
    183. 

  183.             wizard. This option does not have any meaning for silent
    184. 

  184.             uninstalls.</p>
    185. 

  185.           </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>
    186. 

  186.             <p>Controls how the uninstaller handles processes that are still using
    187. 

  187.               Npcap at the time of uninstall. The default value is
    188. 

  188.               <code class="literal">no</code>, which allows the uninstaller to terminate
    189. 

  189.               processes that would block Npcap from being uninstalled. If
    190. 

  190.               <code class="option">/no_kill=yes</code> is specified, then Npcap
    191. 

  191.               uninstaller will fail if there are still applications using Npcap
    192. 

  192.               driver or DLLs.</p>
    193. 

  193. 

  194.             <p>In the default case, <code class="option">/no_kill=no</code>, the
    195. 

  195.               graphical uninstaller will give the user the choice to manually
    196. 

  196.               close the offending programs, have the uninstaller terminate
    197. 

  197.               them, or abort the uninstallation.  In silent mode, Npcap
    198. 

  198.               uninstaller will immediately terminate any command-line processes
    199. 

  199.               that are using Npcap (like a Nmap process that is still
    200. 

  200.               scanning), and wait for at most 15 seconds to gracefully
    201. 

  201.               terminate any GUI processes that are using Npcap (like Wireshark
    202. 

  202.               UI that is still capturing).  <span class="quote">&#8220;<span class="quote">Gracefully</span>&#8221;</span> means
    203. 

  203.               that if you are still capturing via Wireshark, Wireshark UI will
    204. 

  204.               prompt the user about whether to save the current capture before
    205. 

  205.               closing. The user will have 15 seconds to save his session.
    206. 

  206.               <span class="emphasis"><em>Note:</em></span> although Npcap uninstaller won't
    207. 

  207.               terminate Wireshark UI processes immediately, the live capture
    208. 

  208.               stops immediately. This is because Wireshark UI uses command-line
    209. 

  209.               processes named <code class="varname">dumpcap.exe</code> to capture, and
    210. 

  210.               that command-line process will be terminated immediately.</p>
    211. 

  211. 

  212.             <p>If this option is provided on the
    213. 

  213.               <span class="emphasis"><em>installer</em></span> command line, it will be passed to
    214. 

  214.               the Npcap uninstaller when doing an upgrade or
    215. 

  215.               replacement.</p>
    216. 

  216.           </dd></dl></div>
    217. 

  217. 

  218.     </div>
    219. 

  219. 

  220.     <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>
    221. 

  221.       
    222. 

  222. 

  223.       <p>
    224. 

  224.         We may disable or enforce certain options in the installer GUI to make them unselectable. This
    225. 

  225.         usually means that those options can easily cause compatibility issues and are considered
    226. 

  226.         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
    227. 

  227.         parameters, which is described in following sections.
    228. 

  228.       </p>
    229. 

  229. 

  230.       <p>
    231. 

  231.         Fortunately, if a distributor wants to start the Npcap installer GUI and disable or enforce
    232. 

  232.         certain options for reasons like compatibility. It can also use the four value
    233. 

  233.         mechanism by setting the command-line parameters to <code class="option">disabled</code> or <code class="option">enforced</code>.
    234. 

  234.         For example, the following command will start an installer GUI with the
    235. 

  235.         <code class="option">loopback_support</code> option disabled and unselected:
    236. 

  236.       </p>
    237. 

  237. 

  238.       <p>
    239. 

  239.         <span class="command"><strong>npcap-<em class="replaceable"><code>version</code></em>.exe /loopback_support=disabled</strong></span>
    240. 

  240.       </p>
    241. 

  241.     </div>
    242. 

  242. 

  243.   </div>
    244. 

  244. 

  245.   <div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="npcap-platforms"></a>Windows platforms supported</h3></div></div></div>
    246. 

  246. 	  
    247. 

  247. 	  <p>Npcap supports all Windows versions currently supported by Microsoft. Depending on Windows version, the
    248. 

  248. 		  driver may support a different NDIS version, which corresponds to a set of network stack
    249. 

  249. 		  features.</p>
    250. 

  250. 	  <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
    251. 

  251. 			  <p>On <span class="emphasis"><em>Windows 10</em></span>, <span class="emphasis"><em>Windows Server 2016</em></span>, and
    252. 

  252. 				  <span class="emphasis"><em>Windows Server 2019</em></span>, Npcap installs a NDIS 6.50
    253. 

  253. 				  driver.</p></li><li class="listitem">
    254. 

  254. 			  <p>On <span class="emphasis"><em>Windows 8.1</em></span>, <span class="emphasis"><em>Windows 8</em></span>,
    255. 

  255. 				  <span class="emphasis"><em>Windows Server 2012 R2</em></span>, and
    256. 

  256. 				  <span class="emphasis"><em>Windows Server 2012</em></span>,
    257. 

  257. 				  Npcap installs a NDIS 6.30 driver.</p></li><li class="listitem">
    258. 

  258. 			  <p>On <span class="emphasis"><em>Windows 7</em></span> and <span class="emphasis"><em>Windows Server 2008 R2</em></span>, Npcap
    259. 

  259. 				  installs a NDIS 6.20 driver.</p></li></ul></div>
    260. 

  260. 	  <p>Microsoft will end Extended support for Windows versions prior to Windows 10 on January 10, 2023. After
    261. 

  261. 		  that time, new Npcap releases <span class="emphasis"><em>may</em></span> omit support for these operating
    262. 

  262. 		  systems.</p>
    263. 

  263. 	  <p>Npcap can be installed on x86, x86-64, and ARM64. DLLs for the native architecture will be installed, as
    264. 

  264. 		  well as x86 DLLs for applications running in 32-bit emulation.</p>
    265. 

  265.   </div>
    266. 

  266. 

  267.   <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>
    268. 

  268.     
    269. 

  269. 

  270.     <p>
    271. 

  271.       The latest Wireshark has already integrated the support for Npcap's <span class="quote">&#8220;<span class="quote">Monitor Mode</span>&#8221;</span> capture.
    272. 

  272.       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
    273. 

  273.       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>.
    274. 

  274.       This is because Wireshark only recognizes the monitor mode set by itself. So when you turn
    275. 

  275.       on monitor mode outside Wireshark (like in <code class="filename">WlanHelper</code>), Wireshark will not know the adapter
    276. 

  276.       has been in monitor mode, and will still try to capture in Ethernet mode, which will get no traffic.
    277. 

  277. 

  278.       So after all, the correct steps are:
    279. 

  279.     </p>
    280. 

  280. 

  281.     <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Install latest version Wireshark and latest version Npcap with
    282. 

  282.           <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>.
    283. 

  283.           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.
    284. 

  284.           Click the <span class="quote">&#8220;<span class="quote">Start</span>&#8221;</span> button. If you see a horizontal line instead of the checkbox,
    285. 

  285.           then it probably means that your adapter doesn't support monitor mode. You can use the
    286. 

  286.           <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>
    287. 

  287.           packets, you need to specify the decipher key in Wireshark, otherwise
    288. 

  288.           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
    289. 

  289.           will be turned off automatically by Npcap.</p></li></ul></div>
    290. 

  290.   </div>
    291. 

  291. 

  292.   <div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="npcap-qa"></a>Q &amp; A</h3></div></div></div>
    293. 

  293.     
    294. 

  294. 

  295.     <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
    296. 

  296. 	    cause brief interruptions to network connectivity based on the specific changes needed
    297. 

  297. 	    to install the driver in the network stack. This known issue is documented as
    298. 

  298. 	    <a class="ulink" href="" target="_top">issue #53</a> on our tracker.</p>
    299. 

  299. 	<p> A separate issue is a longer interruption in connectivity if the
    300. 

  300. 	    <code class="varname">npcap</code> service is not started, which used to be an installer option.
    301. 

  301. 	    As Microsoft states <a class="ulink" href="https://support.microsoft.com/en-us/kb/2019184" target="_top">here</a>,
    302. 

  302.           <span class="emphasis"><em>an optional NDIS light-weight filter (LWF) driver like Npcap could cause
    303. 

  303.             90-second delay in network availability</em></span>. Some solutions you could try
    304. 

  304.           are: 1) wait for 90 seconds; 2) disable and re-enable the adapter icon in
    305. 

  305.           <span class="command"><strong>ncpa.cpl</strong></span>; 3) reboot. If the network is still unable to connect,
    306. 

  306.           please <a class="ulink" href="http://issues.npcap.org/new?title=Npcap+Bug+Report" target="_top">file a bug report</a>.
    307. 

  307.       </p></li><li class="listitem"><p>Installation fails with error code <code class="varname">0x8004a029</code>:
    308. 

  308.           The cause is that you have <span class="quote">&#8220;<span class="quote">reached the maximum number of network filter
    309. 

  309.             drivers</span>&#8221;</span>, see solution
    310. 

  310.           <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>.
    311. 

  311.       </p></li><li class="listitem"><p>Npcap Loopback Adapter is missing (legacy loopback support):
    312. 

  312.           The legacy Npcap Loopback Adapter is actually a wrapper of Microsoft Loopback Adapter.
    313. 

  313.           Such adapters won't show up in Wireshark if the <code class="varname">Basic Filtering Enging (BFE)</code>
    314. 

  314.           service was not running. To fix this issue, you should start this service at <code class="varname">services.msc</code>
    315. 

  315.           manually and restart the Npcap service by running <span class="command"><strong>net stop npcap</strong></span>
    316. 

  316.           and <span class="command"><strong>net start npcap</strong></span>. See details about this issue
    317. 

  317.           <a class="ulink" href="https://github.com/nmap/nmap/issues/802" target="_top">here</a>.
    318. 

  318.       </p></li><li class="listitem"><p>Npcap only captures TCP handshake and teardown, but not data packets.
    319. 

  319.           Some network adapters support offloading of tasks to free up CPU time for
    320. 

  320.           performance reasons. When this happens, Npcap may not receive all of the
    321. 

  321.           packets, or may receive them in a different form than is actually sent on the
    322. 

  322.           wire. To avoid this issue, you may disable TCP Chimney, IP Checksum
    323. 

  323.           Offloading, and Large Send Offloading in the network adapter properites on
    324. 

  324.           Windows. See details about this issue in
    325. 

  325.           <a class="ulink" href="https://github.com/nmap/nmap/issues/989" target="_top">issue
    326. 

  326.             #989</a> on our tracker.
    327. 

  327.       </p></li></ul></div>
    328. 

  328.   </div>
    329. 

  329. 

  330.   <div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="npcap-issues"></a>Reporting Bugs</h3></div></div></div>
    331. 

  331.     
    332. 

  332. 

  333.     <p>
    334. 

  334.       Please report any bugs or issues about Npcap on
    335. 

  335.       <a class="ulink" href="http://issues.npcap.org/new?title=Npcap+Bug+Report" target="_top">the Nmap Project's Issues tracker</a>.
    336. 

  336.       In your report, please provide your <span class="emphasis"><em>DiagReport</em></span> output, user
    337. 

  337.       software version (e.g. Nmap, Wireshark), steps to reproduce the problem, and other information
    338. 

  338.       you think necessary. If your issue occurs only on a particular OS version (e.g. Win10
    339. 

  339.       1511, 1607), please mention it in the report.
    340. 

  340.     </p>
    341. 

  341. 

  342.     <div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a name="npcap-issues-diagreport"></a>Diagnostic report</h4></div></div></div>
    343. 

  343.       
    344. 

  344. 

  345.       <p>
    346. 

  346.         Npcap has provided a diagnostic utility called <code class="filename">DiagReport</code>.
    347. 

  347.         It provides a lot of information including OS metadata, Npcap related files,
    348. 

  348.         install options, registry values, services, etc. You can simply click the
    349. 

  349.         <code class="filename">C:\Program Files\Npcap\DiagReport.bat</code> file to run <code class="filename">DiagReport</code>.
    350. 

  350.         It will pop up a text report via Notepad (it's stored in: <code class="filename">C:\Program Files\Npcap\DiagReport.txt</code>).
    351. 

  351.         Please always submit it to us if you encounter any issues.
    352. 

  352.       </p>
    353. 

  353. 

  354.     </div>
    355. 

  355.     <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>
    356. 

  356.       
    357. 

  357. 

  358.       <p>
    359. 

  359.         Npcap keeps track of the installation in a log file:
    360. 

  360.         <code class="filename">C:\Program Files\Npcap\install.log</code>. Please submit it
    361. 

  361.         together in your report if you encounter issues during the installation
    362. 

  362.         (e.g. the installer halts).
    363. 

  363.       </p>
    364. 

  364.     </div>
    365. 

  365. 

  366.     <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>
    367. 

  367.       
    368. 

  368. 

  369.       <p>
    370. 

  370.         Npcap keeps track of the driver installation (aka commands run by
    371. 

  371.         <code class="filename">NPFInstall.exe</code>) in a log file:
    372. 

  372.         <code class="filename">C:\Program Files\Npcap\NPFInstall.log</code>, please submit
    373. 

  373.         it together in your report if you encounter issues during the driver
    374. 

  374.         installation or problems with the <span class="quote">&#8220;<span class="quote">Npcap Loopback Adapter</span>&#8221;</span>.
    375. 

  375.       </p>
    376. 

  376. 

  377.       <p>
    378. 

  378.         There's another system-provided driver installation log in:
    379. 

  379.         <code class="filename">C:\Windows\INF\setupapi.dev.log</code>.
    380. 

  380.         If you encounter errors during the driver/service installation, please copy
    381. 

  381.         the Npcap-related lines out and send them together in
    382. 

  382.         your report.
    383. 

  383.       </p>
    384. 

  384.     </div>
    385. 

  385. 

  386.     <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>
    387. 

  387.       
    388. 

  388. 

  389.       <p>
    390. 

  390.         For problems with Npcap's regular operation, you may need to obtain a
    391. 

  391.         debug log from <code class="filename">Packet.dll</code>.  To do this, you will
    392. 

  392.         need a debug build of Npcap.  If you are a Npcap developer, you can build
    393. 

  393.         the <code class="filename">Packet.sln</code> project with the
    394. 

  394.         <code class="varname">_DEBUG_TO_FILE</code> macro defined. If you are an end user,
    395. 

  395.         you can contact the Npcap development team for the latest Npcap debug
    396. 

  396.         build.  The debugging process will continue to append to the debug log
    397. 

  397.         (<code class="filename">C:\Program Files\Npcap\Packet.log</code>), so you may want
    398. 

  398.         to delete it after an amount of time, or save your output to another
    399. 

  399.         place before it gets too large.
    400. 

  400.       </p>
    401. 

  401.     </div>
    402. 

  402. 

  403.     <div class="sect3"><div class="titlepage"><div><div><h4 class="title"><a name="npcap-issues-driver-log"></a>Driver log</h4></div></div></div>
    404. 

  404.       
    405. 

  405. 

  406.       <p>
    407. 

  407.         If there is an issue with the Npcap driver, you can open an
    408. 

  408.         <span class="emphasis"><em>Administrator</em></span> command prompt,  enter <span class="command"><strong>sc query
    409. 

  409.           npcap</strong></span> to query the driver status and <span class="command"><strong>net start
    410. 

  410.           npcap</strong></span> to start the driver (replace
    411. 

  411.         <em class="replaceable"><code>npcap</code></em> with <em class="replaceable"><code>npf</code></em> if you
    412. 

  412.         installed Npcap in <span class="quote">&#8220;<span class="quote">WinPcap Compatible Mode</span>&#8221;</span>).  The command
    413. 

  413.         output will inform you whether there's an error. If the driver is running
    414. 

  414.         well, but the issue still exists, then you may need to check the driver's
    415. 

  415.         log. Normal Npcap releases don't switch on the driver log function for
    416. 

  416.         performance. Contact the Npcap development team to obtain a driver-debug
    417. 

  417.         version of the Npcap installer.  When you have got an appropriate
    418. 

  418.         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>
    419. 

  419.         to read the Windows kernel log (which contains our driver log).  You may
    420. 

  420.         need to turn on DbgView before installing Npcap, if the error occurs when
    421. 

  421.         the driver loads. When done, save the DbgView output to a file and submit
    422. 

  422.         it in your report.
    423. 

  423.       </p>
    424. 

  424.     </div>
    425. 

  425.     <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>
    426. 

  426.       
    427. 

  427. 

  428.       <p>
    429. 

  429.         If you encountered BSoD when using Npcap, please attach the minidump
    430. 

  430.         file (in <code class="filename">C:\Windows\Minidump\</code>) to your report
    431. 

  431.         together with the Npcap version. We may ask you to provide the full
    432. 

  432.         dump (<code class="filename">C:\Windows\MEMORY.DMP</code>) for further troubleshooting.
    433. 

  433.       </p>
    434. 

  434.     </div>
    435. 

  435.   </div>
    436. 

  436. 

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    438.