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nping/docs/nping-man.xml
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nnposter
Remove a comment leftover. Fixes #2858
13 июн 2024, 03:09
13 июн 2024, 03:091daf966
<refentry id="npingman">
  <refmeta>
    <refentrytitle>nping</refentrytitle>
    <manvolnum>1</manvolnum>
    <refmiscinfo class="source">Nping</refmiscinfo>
    <refmiscinfo class="manual">Nping Reference Guide</refmiscinfo>
  </refmeta>
  <refnamediv id="nping-man-name">
    <refname>nping</refname>
    <refpurpose>Network packet generation tool / ping utility</refpurpose>
  </refnamediv>
  <!-- body begins here -->
  <refsynopsisdiv id="nping-man-synopsis">
    <cmdsynopsis sepchar=" ">
      <command>nping</command>
      <arg choice="opt" rep="norepeat">
        <replaceable>Options</replaceable>
      </arg>
      <arg choice="req" rep="norepeat">
        <replaceable>targets</replaceable>
      </arg>
    </cmdsynopsis>
  </refsynopsisdiv>
  <refsect1 id="nping-man-description">
    <title>Description</title>
    <indexterm><primary>Nping</primary><secondary>description of</secondary></indexterm>
    <web>
    <note><para>This document describes the very latest version of
    Nping available from <ulink url="https://nmap.org/nping"/> Please
    ensure you are using the latest version before reporting that a
    feature doesn't work as described.</para></note>
    </web>
    <para>Nping is an open-source tool for network packet generation,
    response analysis and response time measurement. Nping allows
    users to generate network packets of a wide range of protocols,
    letting them tune virtually any field of the protocol
    headers. While Nping can be used as a simple ping utility to
    detect active hosts, it can also be used as a raw packet generator
    for network stack stress tests, ARP poisoning, Denial of Service
    attacks, route tracing, and other purposes.</para>

     <para>Additionally, Nping offers a special mode of operation called
     the "Echo Mode", that lets users see how the generated probes change
     in transit, revealing the differences between the transmitted packets and
     the packets received at the other end. See section "Echo Mode" for details.
     </para>

    <para>The output from Nping is a list of the packets that are being sent
    and received. The level of detail depends on the options used.</para>
<!--
    <para>Additionally, Nping can provide further information on targets,
    including reverse DNS names and MAC addresses.</para>
-->

    <para>A typical Nping execution is shown in <xref linkend="nping-man-ex-repping" xrefstyle="select: label nopage"/>.  The only Nping arguments used in
    this example are <option>-c</option>, to specify the number of times to
    target each host, <option>--tcp</option> to specify TCP Probe Mode,
    <option>-p 80,433</option> to specify the target ports; and then the two
    target hostnames.</para>

<example id="nping-man-ex-repping"><title>A representative Nping execution</title>
<indexterm><primary><option>-c</option> (Nping option)</primary><secondary>example of</secondary></indexterm>
<indexterm><primary><option>--tcp</option> (Nping option)</primary><secondary>example of</secondary></indexterm>
<indexterm><primary><option>-p</option> (Nping option)</primary><secondary>example of</secondary></indexterm>
<screen format="linespecific">
# <userinput>nping -c 1 --tcp -p 80,433 scanme.nmap.org google.com</userinput>

Starting Nping ( https://nmap.org/nping )
SENT (0.0120s) TCP 96.16.226.135:50091 &gt; 64.13.134.52:80 S ttl=64 id=52072 iple<continuation/>n=40  seq=1077657388 win=1480 
RCVD (0.1810s) TCP 64.13.134.52:80 &gt; 96.16.226.135:50091 SA ttl=53 id=0 iplen=4<continuation/>4  seq=4158134847 win=5840 &lt;mss 1460&gt;
SENT (1.0140s) TCP 96.16.226.135:50091 &gt; 74.125.45.100:80 S ttl=64 id=13932 ipl<continuation/>en=40  seq=1077657388 win=1480 
RCVD (1.1370s) TCP 74.125.45.100:80 &gt; 96.16.226.135:50091 SA ttl=52 id=52913 ip<continuation/>len=44  seq=2650443864 win=5720 &lt;mss 1430&gt;
SENT (2.0140s) TCP 96.16.226.135:50091 &gt; 64.13.134.52:433 S ttl=64 id=8373 iple<continuation/>n=40  seq=1077657388 win=1480 
SENT (3.0140s) TCP 96.16.226.135:50091 &gt; 74.125.45.100:433 S ttl=64 id=23624 ip<continuation/>len=40  seq=1077657388 win=1480 

Statistics for host scanme.nmap.org (64.13.134.52):
 |  Probes Sent: 2 | Rcvd: 1 | Lost: 1  (50.00%)
 |_ Max rtt: 169.720ms | Min rtt: 169.720ms | Avg rtt: 169.720ms
Statistics for host google.com (74.125.45.100):
 |  Probes Sent: 2 | Rcvd: 1 | Lost: 1  (50.00%)
 |_ Max rtt: 122.686ms | Min rtt: 122.686ms | Avg rtt: 122.686ms
Raw packets sent: 4 (160B) | Rcvd: 2 (92B) | Lost: 2 (50.00%)
Tx time: 3.00296s | Tx bytes/s: 53.28 | Tx pkts/s: 1.33
Rx time: 3.00296s | Rx bytes/s: 30.64 | Rx pkts/s: 0.67
Nping done: 2 IP addresses pinged in 4.01 seconds
</screen>
</example>

<!-- This para is a bit jumbled together for man page rendering reasons -->
<para>The newest version of Nping can be obtained with Nmap at <ulink url="https://nmap.org"/>.  The newest version of this man page
is available at <ulink url="https://nmap.org/book/nping-man.html"/>.</para>
  </refsect1>

  <refsect1 id="nping-man-briefoptions">
    <title>Options Summary</title>


<para>This options summary is printed when Nping is run
with no arguments. It helps people remember the most common options,
but is no substitute for the in-depth documentation in the rest of this manual.
Some obscure options aren't even included here.</para>

<!-- sortas="#" puts it before the entries that start with '-' in the options
     section. -->
<indexterm class="startofrange" id="nping-usage-indexterm"><primary sortas="#">summary of options (Nping)</primary></indexterm>
<indexterm class="startofrange" id="nping-usage-nping-indexterm"><primary>command-line options</primary><secondary>of Nping</secondary></indexterm>

&nping-usage;

<indexterm class="endofrange" startref="nping-usage-nping-indexterm"/>
<indexterm class="endofrange" startref="nping-usage-indexterm"/>

  </refsect1>


  <refsect1 id="nping-man-target-specification">
    <title>Target Specification</title>
    <indexterm><primary>target specification</primary><secondary>in Nping</secondary></indexterm>

     <para>Everything on the Nping command line that isn't an option or an
           option argument is treated as a target host specification. Nping
           uses the same syntax for target specifications that Nmap does. The
           simplest case is a single target given by IP address or hostname.
     </para>


     <para>Nping supports
           CIDR-style<indexterm><primary>CIDR (Classless Inter-Domain Routing)</primary></indexterm>
           addressing. You can append <literal>/<replaceable>numbits</replaceable></literal> to an
           IPv4 address or hostname and Nping will send probes to every IP
           address for which the first <replaceable>numbits</replaceable> are the same as for the
           reference IP or hostname given. For example, <literal>192.168.10.0/24</literal> would
           send probes to the 256 hosts between 192.168.10.0
           (binary: <literal>11000000 10101000 00001010 00000000</literal>)
           and 192.168.10.255
           (binary: <literal>11000000 10101000 00001010 11111111</literal>),
           inclusive. <literal>192.168.10.40/24</literal> would ping exactly the same targets.
           Given that the host scanme.nmap.org<indexterm><primary>scanme.nmap.org</primary></indexterm>
           is at the IP address 64.13.134.52, the specification
           <literal>scanme.nmap.org/16</literal> would send probes to the 65,536 IP addresses
           between 64.13.0.0 and 64.13.255.255. The smallest allowed value is
           <literal>/0</literal>, which targets the whole Internet. The largest value is <literal>/32</literal>,
           which targets just the named host or IP address because all address
           bits are fixed.
     </para>

    <indexterm><primary>address ranges</primary></indexterm>
     <para>CIDR notation is short but not always flexible enough.  For example,
           you might want to send probes to 192.168.0.0/16 but skip any IPs
           ending with .0 or .255 because they may be used as subnet network
           and broadcast addresses. Nping supports this through octet range
           addressing. Rather than specify a normal IP address, you can specify
           a comma-separated list of numbers or ranges for each octet. For
           example, <literal>192.168.0-255.1-254</literal> will skip all addresses in the range
           that end in .0 or .255, and <literal>192.168.3-5,7.1</literal> will target the four
           addresses 192.168.3.1, 192.168.4.1, 192.168.5.1, and 192.168.7.1.
           Either side of a range may be omitted; the default values are 0 on
           the left and 255 on the right. Using
           <literal>-</literal> by itself is the same as <literal>0-255</literal>,
           but remember to use <literal>0-</literal> in the first octet so the target
           specification doesn't look like a command-line option. Ranges need
           not be limited to the final octets: the specifier <literal>0-.-.13.37</literal> will send probes
           to all IP addresses on the Internet ending in .13.37. This sort of
           broad sampling can be useful for Internet surveys and research.
     </para>

     <para>IPv6 addresses can only be specified by their fully qualified IPv6
           address or hostname. CIDR and octet ranges aren't supported for
           IPv6 because they are rarely useful.</para>

     <para>Nping accepts multiple host specifications on the command line,
           and they don't need to be the same type. The command
           <command>nping scanme.nmap.org
           192.168.0.0/8 10.0.0,1,3-7.-</command> does what you would expect.
     </para>

  </refsect1>


  <refsect1 id="nping-man-option-specification">
    <title>Option Specification</title>

     <para>
        Nping is designed to be very flexible and fit a wide variety of needs.
        As with most command-line tools, its behavior can be adjusted using
        command-line options. These general principles apply to option
        arguments, unless stated otherwise.
     </para>

     <para>
        Options that take integer numbers can accept values specified in
        decimal, octal or hexadecimal base. When a number starts with <literal>0x</literal>,
        it will be treated as hexadecimal; when it simply starts with <literal>0</literal>, it
        will be treated as octal. Otherwise, Nping will assume the number has
        been specified in base 10. Virtually all numbers that can be supplied
        from the command line are unsigned so, as a general rule, the minimum
        value is zero. Users may also specify the word <literal>random</literal> or <literal>rand</literal> to
        make Nping generate a random value within the expected range.
     </para>

     <para>
        IP addresses may be given as IPv4 addresses (e.g.
        <literal>192.168.1.1</literal>), IPv6 addresses (e.g.
        <literal>2001:db8:85a3::8e4c:760:7146</literal>), or hostnames, which
        will be resolved using the default DNS server configured in the host
        system.
     </para>

     <para>
        Options that take MAC addresses accept the usual colon-separated 6 hex
        byte format (e.g. <literal>00:50:56:d4:01:98</literal>). Hyphens may also be used instead
        of colons (e.g. <literal>00-50-56-c0-00-08</literal>). The special
        word <literal>random</literal> or <literal>rand</literal> sets a random
        address and the word <literal>broadcast</literal>
        or <literal>bcast</literal> sets ff:ff:ff:ff:ff:ff. 
     </para> 

  </refsect1>


   <refsect1 id="nping-man-general-operation">
    <title>General Operation</title>
    <indexterm><primary>general operation</primary></indexterm>

     <para>Unlike other ping and packet generation tools, Nping supports
           multiple target host and port specifications. While
           this provides great flexibility, it is not obvious how Nping handles
           situations where there is more than one host and/or more than one
           port to send probes to. This section explains how Nping behaves in
           these cases.
     </para>

     <para>
            When multiple target hosts are specified, Nping rotates among them
            in round-robin fashion. This gives slow hosts more time to send
            their responses before another probe is sent to them. Ports are
            also scheduled using round robin. So, unless only one port is
            specified, Nping never sends two probes to the same target host and
            port consecutively.
     </para>

     <para>
            The loop around targets is the <quote>inner loop</quote> and the
            loop around ports is the <quote>outer loop</quote>. All targets
            will be sent a probe for a given port before moving on to the next
            port. Between probes, Nping waits a configurable amount of time
            called the <quote>inter-probe delay</quote>, which is controlled by
            the <option>--delay</option> option. These examples show how it
            works.
     </para>

     <variablelist>
       <varlistentry>
         <term>
           <para>One target, three ports, and two rounds.</para>
         </term>
         <listitem>
<screen>
# <userinput>nping --tcp -c 2 1.1.1.1 -p 100-102</userinput>

Starting Nping ( https://nmap.org/nping )
SENT (0.0210s) TCP 192.168.1.77 &gt; 1.1.1.1:100
SENT (1.0230s) TCP 192.168.1.77 &gt; 1.1.1.1:101
SENT (2.0250s) TCP 192.168.1.77 &gt; 1.1.1.1:102
SENT (3.0280s) TCP 192.168.1.77 &gt; 1.1.1.1:100
SENT (4.0300s) TCP 192.168.1.77 &gt; 1.1.1.1:101
SENT (5.0320s) TCP 192.168.1.77 &gt; 1.1.1.1:102
</screen>
         </listitem>
       </varlistentry>
       <varlistentry>
         <term>
           <para>Three targets, one port, and two rounds.</para>
         </term>
         <listitem>
<screen>
# <userinput>nping --tcp -c 2 1.1.1.1 2.2.2.2 3.3.3.3 -p 8080</userinput>

Starting Nping ( https://nmap.org/nping )
SENT (0.0230s) TCP 192.168.0.21 &gt; 1.1.1.1:8080
SENT (1.0240s) TCP 192.168.0.21 &gt; 2.2.2.2:8080
SENT (2.0260s) TCP 192.168.0.21 &gt; 3.3.3.3:8080
SENT (3.0270s) TCP 192.168.0.21 &gt; 1.1.1.1:8080
SENT (4.0290s) TCP 192.168.0.21 &gt; 2.2.2.2:8080
SENT (5.0310s) TCP 192.168.0.21 &gt; 3.3.3.3:8080
</screen>
         </listitem>
       </varlistentry>
       <varlistentry>
         <term>
           <para>Three hosts, three ports, one round, inter-probe delay of 500&nbsp;ms.</para>
         </term>
         <listitem>
<screen>
# <userinput>nping --tcp -c 1 --delay 500ms 1.1.1.1 2.2.2.2 3.3.3.3 -p 137-139</userinput>

Starting Nping ( https://nmap.org/nping )
SENT (0.0230s) TCP 192.168.0.21 &gt; 1.1.1.1:137
SENT (0.5250s) TCP 192.168.0.21 &gt; 2.2.2.2:137
SENT (1.0250s) TCP 192.168.0.21 &gt; 3.3.3.3:137
SENT (1.5280s) TCP 192.168.0.21 &gt; 1.1.1.1:138
SENT (2.0280s) TCP 192.168.0.21 &gt; 2.2.2.2:138
SENT (2.5310s) TCP 192.168.0.21 &gt; 3.3.3.3:138
SENT (3.0300s) TCP 192.168.0.21 &gt; 1.1.1.1:139
SENT (3.5330s) TCP 192.168.0.21 &gt; 2.2.2.2:139
SENT (4.0330s) TCP 192.168.0.21 &gt; 3.3.3.3:139
</screen>
         </listitem>
       </varlistentry>
     </variablelist>    
   </refsect1>


  <refsect1 id="nping-man-probe-modes">
    <title>Probe Modes</title>
    <indexterm class="startofrange" id="nping-man-probe-modes-indexterm"><primary>probe modes</primary></indexterm>

    <para>Nping supports a wide variety of protocols. Although in some cases
          Nping can automatically determine the mode from the options used, it
          is generally a good idea to specify it explicitly.
    </para>

    <variablelist>

      <varlistentry>
        <term>
        <option>--tcp-connect</option> (TCP Connect mode)
          <indexterm><primary><option>--tcp-connect</option> (Nping option)</primary></indexterm>
          <indexterm><primary>TCP connect</primary><secondary>in Nping</secondary></indexterm>
          <indexterm><primary>TCP connect</primary><seealso>connect scan</seealso></indexterm>
        </term>
        <listitem>
         <para>TCP connect mode is the default mode when a user does not have
               raw packet privileges. Instead of writing raw packets as most
               other modes do, Nping asks the underlying operating system to
               establish a connection with the target machine and port by
               issuing the <literal>connect</literal> system call. This is the same high-level
               system call that web browsers, P2P clients, and most other
               network-enabled applications use to establish a connection.
               It is part of a programming interface known as the Berkeley
               Sockets API. Rather than read raw packet responses off the wire,
               Nping uses this API to obtain status information on each
               connection attempt. For this reason, you will not be able to
               see the contents of the packets that are sent or received but
               only status information about the TCP connection establishment
               taking place.
         </para>

        </listitem>
      </varlistentry>


      <varlistentry>
        <term>
        <option>--tcp</option> (TCP mode)
          <indexterm><primary><option>--tcp</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
         <para>TCP is the mode that lets users create and send any kind of TCP
               packet. TCP packets are sent embedded in IP packets that
               can also be tuned. This mode can be used for many different
               purposes. For example you could try to discover open ports by
               sending TCP SYN messages without completing the three-way
               handshake. This technique is often referred to as half-open
               scanning, because you don't open a full TCP connection.
               You send a SYN packet, as if you are going to open a real
               connection and then wait for a response. A SYN/ACK indicates
               the port is open, while a RST indicates it's closed. If no
               response is received one could assume that some intermediate
               network device is filtering the responses. Another use could be
               to see how a remote TCP/IP stack behaves when it receives a
               non-RFC-compliant packet, like one with both SYN and
               RST flags set. One could also do some evil by creating custom
               RST packets using an spoofed IP address with the intent of
               closing an active TCP connection.
         </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term>
        <option>--udp</option> (UDP mode)
          <indexterm><primary><option>--udp</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
         <para>UDP mode can have two different behaviours. Under normal 
               circumstances, it lets users create custom IP/UDP packets. 
               However, if Nping is run by a user without raw packet privileges
               and no changes to the default protocol headers are requested, 
               then Nping enters the unprivileged UDP mode which basically sends
               UDP packets to the specified target hosts and ports using the 
               <literal>sendto</literal> system call. Note that in this unprivileged mode it is 
               not possible to see low-level header information of the packets
               on the wire but only status information about the amount of bytes
               that are being transmitted and received. UDP mode can be used to 
               interact with any UDP-based server. Examples are DNS servers, 
               streaming servers, online gaming servers, and
               port knocking/single-packet<indexterm><primary>port knocking</primary></indexterm>
               authorization daemons.
          </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term>
        <option>--icmp</option> (ICMP mode)
          <indexterm><primary><option>--icmp</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
         <para>ICMP mode is the default mode when the user runs Nping with
               raw packet privileges. Any kind of ICMP message can be created.
               The default ICMP type is Echo, i.e., ping. ICMP mode can be used
               for many different purposes, from a simple request for a
               timestamp or a netmask to the transmission of fake destination
               unreachable messages, custom redirects, and router
               advertisements.
          </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term>
        <option>--arp</option> (ARP/RARP mode)
          <indexterm><primary><option>--arp</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
         <para>ARP lets you create and send a few different ARP-related packets.
               These include ARP, RARP, DRARP, and InARP requests and replies.
               This mode can ban be used to perform low-level host discovery,
               and conduct ARP-cache poisoning attacks.</para>
        </listitem>
      </varlistentry>



      <varlistentry>
        <term>
        <option>--traceroute</option> (Traceroute mode)
          <indexterm><primary><option>--tcp-connect</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
         <para>Traceroute is not a mode by itself but a complement to
               TCP, UDP, and ICMP modes. When this option is specified Nping
               will set the IP TTL value of the first probe to 1. When the
               next router receives the packet it will drop it due to
               the expiration of the TTL and it will generate an ICMP
               destination unreachable message. The next probe will have a TTL
               of 2 so now the first router will forward the packet while the
               second router will be the one that drops the packet and
               generates the ICMP message. The third probe will have a TTL value
               of 3 and so on. By examining the source addresses of all
               those ICMP Destination Unreachable messages it is possible to
               determine the path that the probes take until they reach their
               final destination.
          </para>

        </listitem>
      </varlistentry>

    </variablelist>
    <indexterm class="endofrange" startref="nping-man-probe-modes-indexterm"/>
  </refsect1>



<!-- TCP CONNECT MODE ****************************************************** -->
  <refsect1 id="nping-man-tcp-connect-mode">
  <title>TCP Connect Mode</title>

    <variablelist>

      <varlistentry>
        <term>          
          <option>-p <replaceable>port_spec</replaceable></option>,
          <option>--dest-port <replaceable>port_spec</replaceable></option> (Target ports)
          <indexterm significance="preferred"><primary><option>--dest-port</option> (Nping option)</primary></indexterm>
          <indexterm significance="preferred"><primary><option>-p</option> (Nping option)</primary><see><option>--dest-port</option></see></indexterm>
        </term>
        <listitem>
          <para>
           This option specifies which ports you want to try to connect to.  
           It can be a single port, a comma-separated list of 
           ports (e.g. <literal>80,443,8080</literal>), a range
           (e.g. <literal>1-1023</literal>), and any combination
           of those (e.g. <literal>21-25,80,443,1024-2048</literal>).
           The beginning and/or end values
           of a range may be omitted, causing Nping to use 1 and 65535, 
           respectively. So you can specify <literal>-p-</literal> to target ports from 1 through 
           65535. Using port zero is allowed if you specify it explicitly.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>          
          <option>-g <replaceable>portnumber</replaceable></option>,
          <option>--source-port <replaceable>portnumber</replaceable></option> (Spoof source port)
          <indexterm significance="preferred"><primary><option>--source-port</option> (Nping option)</primary></indexterm>
          <indexterm significance="preferred"><primary><option>-g</option> (Nping option)</primary><see><option>--source-port</option></see></indexterm>
        </term>
        <listitem>
          <para>
           This option asks Nping to use the specified port as source port for
           the TCP connections. Note that this might not work on all systems or
           may require root privileges. Specified value must be an integer in
           the range [0&ndash;65535].
        </para>
        </listitem>
      </varlistentry>


    </variablelist>
   </refsect1>




<!-- TCP MODE ************************************************************** -->
  <refsect1 id="nping-man-tcp-mode">
  <title>TCP Mode</title>

    <variablelist>


      <varlistentry>
        <term>          
          <option>-p <replaceable>port_spec</replaceable></option>,
          <option>--dest-port <replaceable>port_spec</replaceable></option> (Target ports)
        </term>
        <listitem>
          <para>
           This option specifies which destination ports you want to send
           probes to. It can be a single port, a comma-separated list of 
           ports (e.g. <literal>80,443,8080</literal>), a range
           (e.g. <literal>1-1023</literal>), and any combination
           of those (e.g. <literal>21-25,80,443,1024-2048</literal>).
           The beginning and/or end values
           of a range may be omitted, causing Nping to use 1 and 65535, 
           respectively. So you can specify <literal>-p-</literal> to target ports from 1 through 
           65535. Using port zero is allowed if you specify it explicitly.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>          
          <option>-g <replaceable>portnumber</replaceable></option>,
          <option>--source-port <replaceable>portnumber</replaceable></option> (Spoof source port)
        </term>
        <listitem>
          <para>
           This option asks Nping to use the specified port as source port for
           the TCP connections. Note that this might not work on all systems or
           may require root privileges. Specified value must be an integer in
           the range [0&ndash;65535].
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
        <option>--seq <replaceable>seqnumber</replaceable></option> (Sequence Number)
        <indexterm significance="preferred"><primary><option>--seq</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           Specifies the TCP sequence number. In SYN packets this is the initial
           sequence number (ISN). In a normal transmission this corresponds to 
           the sequence number of the first byte of data in the segment.
           <replaceable>seqnumber</replaceable> must be a number in the range 
           [0&ndash;4294967295].
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term>
        <option>--flags <replaceable>flags</replaceable></option> (TCP Flags)
        <indexterm significance="preferred"><primary><option>--flags</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option specifies which flags should be set in the TCP packet. 
           <replaceable>flags</replaceable> may be specified in three different
           ways:
          </para>

          <orderedlist spacing="compact">
            <listitem>
              <para>As a comma-separated list of flags, e.g. <option>--flags syn,ack,rst</option></para>
            </listitem>
            <listitem>
              <para>As a list of one-character flag initials, e.g. <option>--flags SAR</option> tells Nping to set flags SYN, ACK, and RST.</para>
            </listitem>
            <listitem>
              <para>As an 8-bit hexadecimal number, where the supplied number
              is the exact value that will be placed in the flags field of the
              TCP header. The number should start with the prefix
              <literal>0x</literal> and should be in the range
              [0x00&ndash;0xFF], e.g. <literal>--flags 0x20</literal> sets the
              URG flag as 0x20 corresponds to binary 00100000 and the URG flag
              is represented by the third bit.</para>
            </listitem>
          </orderedlist>

          <para>
            There are 8 possible flags to set:
            <literal>CWR</literal>,
            <literal>ECN</literal>,
            <literal>URG</literal>,
            <literal>ACK</literal>,
            <literal>PSH</literal>,
            <literal>RST</literal>,
            <literal>SYN</literal>, and
            <literal>FIN</literal>.
            The special value <literal>ALL</literal> means to set all flags. 
            <literal>NONE</literal> means to set no flags. It is important that
            if you don't want any flag to be set, you request it explicitly
            because in some cases the SYN flag may be set by default. Here is a
            brief description of the meaning of each flag:
          </para>

          <variablelist>
            <varlistentry>
              <term>
              CWR (Congestion Window Reduced)
              <indexterm><primary>CWR (TCP flag)</primary></indexterm>
              </term>
              <listitem>
              <para>
              Set by an ECN-Capable sender
              when it reduces its congestion window (due to a retransmit
              timeout, a fast retransmit or in response to an ECN
              notification.
              </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>
              ECN (Explicit Congestion Notification)
              <indexterm><primary>ECN (TCP flag)</primary></indexterm>
              </term>
              <listitem>
              <para>
              During the three-way
              handshake it indicates that sender is capable of performing
              explicit congestion notification. Normally it means that a
              packet with the IP Congestion Experienced flag set was received
              during normal transmission. See
              RFC 3168<indexterm><primary>RFC 3168</primary></indexterm>
              for more information.
              </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>
              URG (Urgent)
              <indexterm><primary>URG (TCP flag)</primary></indexterm>
              </term>
              <listitem>
              <para>
              Segment is urgent and the urgent pointer field 
              carries valid information.
              </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>
              ACK (Acknowledgement)
              <indexterm><primary>ACK (TCP flag)</primary></indexterm>
              </term>
              <listitem>
              <para>
              The segment carries an acknowledgement
              and the value of the acknowledgement number field is valid and
              contains the next sequence number that is expected from the
              receiver.
              </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>
              PSH (Push)
              <indexterm><primary>PSH (TCP flag)</primary></indexterm>
              </term>
              <listitem>
              <para>
              The data in this segment should be immediately
              pushed to the application layer on arrival.
              </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>
              RST (Reset)
              <indexterm><primary>RST (TCP flag)</primary></indexterm>
              </term>
              <listitem>
              <para>
              There was some problem and the sender wants to
              abort the connection.
              </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>
              SYN (Synchronize)
              <indexterm><primary>SYN (TCP flag)</primary></indexterm>
              </term>
              <listitem>
              <para>
              The segment is a request to synchronize
              sequence numbers and establish a connection. The sequence
              number field contains the sender's initial sequence
              number.
              </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>
              FIN (Finish)
              <indexterm><primary>FIN (TCP flag)</primary></indexterm>
              </term>
              <listitem>
              <para>
              The sender wants to close the connection.
              </para>
              </listitem>
            </varlistentry>
          </variablelist>

        </listitem>
      </varlistentry>




      <varlistentry>
        <term>
        <option>--win <replaceable>size</replaceable></option> (Window Size)
        <indexterm significance="preferred"><primary><option>--win</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           Specifies the TCP window size, this is, the number of octets the
           sender of the segment is willing to accept from the receiver at one
           time. This is usually the size of the reception buffer that the OS 
           allocates for a given connection. <replaceable>size</replaceable> 
           must be a number in the range [0&ndash;65535].
          </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term>
        <option>--badsum</option> (Invalid Checksum)
        <indexterm significance="preferred"><primary><option>--badsum</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           Asks Nping to use an invalid TCP checksum for the packets sent to 
           target hosts. Since virtually all host IP stacks properly drop these
           packets, any responses received are likely coming from a firewall or 
           an IDS that didn't bother to verify the checksum. For more
           details on this technique, see
           <ulink url="https://nmap.org/p60-12.html"/>.
        </para>
        </listitem>
      </varlistentry>

    </variablelist>
   </refsect1>




<!-- UDP MODE ************************************************************** -->
  <refsect1 id="nping-man-udp-mode">
  <title>UDP Mode</title>


    <variablelist>

      <varlistentry>
        <term>          
          <option>-p <replaceable>port_spec</replaceable></option>,
          <option>--dest-port <replaceable>port_spec</replaceable></option> (Target ports)
          <indexterm significance="preferred"><primary><option>--dest-port</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option specifies which ports you want UDP datagrams to be sent to.
           It can be a single port, a comma-separated list of 
           ports (e.g. <literal>80,443,8080</literal>), a range
           (e.g. <literal>1-1023</literal>), and any combination
           of those (e.g. <literal>21-25,80,443,1024-2048</literal>).
           The beginning and/or end values
           of a range may be omitted, causing Nping to use 1 and 65535, 
           respectively. So you can specify <literal>-p-</literal> to target ports from 1 through 
           65535. Using port zero is allowed if you specify it explicitly.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>          
          <option>-g <replaceable>portnumber</replaceable></option>,
          <option>--source-port <replaceable>portnumber</replaceable></option> (Spoof source port)
          <indexterm significance="preferred"><primary><option>--source-port</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option asks Nping to use the specified port as source port for
           the transmitted datagrams. Note that this might not work on all systems or
           may require root privileges. Specified value must be an integer in
           the range [0&ndash;65535].
        </para>
        </listitem>
      </varlistentry>
  

      <varlistentry>
        <term>
        <option>--badsum</option> (Invalid Checksum)
        </term>
        <listitem>
          <para>
           Asks Nping to use an invalid UDP checksum for the packets sent to 
           target hosts. Since virtually all host IP stacks properly drop these
           packets, any responses received are likely coming from a firewall or 
           an IDS that didn't bother to verify the checksum. For more
           details on this technique, see
           <ulink url="https://nmap.org/p60-12.html"/>.
        </para>
        </listitem>
      </varlistentry>

    </variablelist>
   </refsect1>

  


<!-- ICMP MODE ************************************************************* -->
  <refsect1 id="nping-man-icmp-mode">
  <title>ICMP Mode</title>


    <variablelist>

      <varlistentry>
        <term>          
          <option>--icmp-type <replaceable>type</replaceable></option> (ICMP type)
          <indexterm significance="preferred"><primary><option>--icmp-type</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option specifies which type of ICMP messages should be
           generated. <replaceable>type</replaceable> can be supplied in
           two different ways. You can use the
           <ulink url="http://www.iana.org/assignments/icmp-parameters">official type numbers assigned by IANA</ulink>
           (e.g. <option>--icmp-type 8</option> for ICMP Echo Request), or you
           can use any of the mnemonics listed in
           <xref linkend="nping-man-icmp-types"/>.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term>          
          <option>--icmp-code <replaceable>code</replaceable></option> (ICMP code)
          <indexterm significance="preferred"><primary><option>--icmp-code</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option specifies which ICMP code should be included in 
           the generated ICMP messages. <replaceable>code</replaceable> can be
           supplied in two different ways. You can use the
           <ulink url="http://www.iana.org/assignments/icmp-parameters">official code numbers assigned by IANA</ulink>
           (e.g. <option>--icmp-code 1</option> for Fragment Reassembly Time
           Exceeded), or you can use any of the mnemonics listed in
           <xref linkend="nping-man-icmp-codes"/>.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term>          
          <option>--icmp-id <replaceable>id</replaceable></option> (ICMP identifier)
          <indexterm significance="preferred"><primary><option>--icmp-id</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option specifies the value of the identifier used in some of 
           the ICMP messages. In general it is used to match request and 
           reply messages. <replaceable>id</replaceable> must be a number in 
           the range [0&ndash;65535].
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term>          
          <option>--icmp-seq <replaceable>seq</replaceable></option> (ICMP sequence)
          <indexterm significance="preferred"><primary><option>--icmp-seq</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option specifies the value of the sequence number field used 
           in some ICMP messages. In general it is used to match request and 
           reply messages. <replaceable>id</replaceable> must be a number in 
           the range [0&ndash;65535].
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term>          
          <option>--icmp-redirect-addr <replaceable>addr</replaceable></option> (ICMP Redirect address)
          <indexterm significance="preferred"><primary><option>--icmp-redirect-addr</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option sets the address field in ICMP Redirect messages. In 
           other words, it sets the IP address of the router that should be 
           used when sending IP datagrams to the original destination. 
           <replaceable>addr</replaceable> can be either an IPv4 address
           or a hostname.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term>          
          <option>--icmp-param-pointer <replaceable>pointer</replaceable></option> (ICMP Parameter Problem pointer)
          <indexterm significance="preferred"><primary><option>--icmp-param-pointer</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option specifies the pointer that indicates the location of 
           the problem in ICMP Parameter Problem messages. <replaceable>pointer</replaceable>
           should be a number in the range [0&ndash;255]. Normally this option is
           only used when ICMP code is set to 0 ("Pointer indicates the error").
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term>          
          <option>--icmp-advert-lifetime <replaceable>ttl</replaceable></option> (ICMP Router Advertisement Lifetime)
          <indexterm significance="preferred"><primary><option>--icmp-advert-lifetime</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option specifies the router advertisement lifetime, this is, 
           the number of seconds the information carried in an ICMP Router
           Advertisement can be considered valid for. <replaceable>ttl</replaceable>
           must be a positive integer in the range [0&ndash;65535].
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term>          
          <option>--icmp-advert-entry <replaceable>addr</replaceable>,<replaceable>pref</replaceable></option> (ICMP Router Advertisement Entry)
          <indexterm significance="preferred"><primary><option>--icmp-advert-entry</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option adds a Router Advertisement entry to an ICMP Router
           Advertisement message. The parameter must be two
           values separated by a comma. <replaceable>addr</replaceable> is 
           the router's IP and can be specified either as an IP address in 
           dot-decimal notation or as a hostname. <replaceable>pref</replaceable>
           is the preference level for the specified IP. It must be a number
           in the range [0&ndash;4294967295]. An example is
           <option>--icmp-advert-entry 192.168.128.1,3</option>.
        </para>
        </listitem>
      </varlistentry>



      <varlistentry>
        <term>          
          <option>--icmp-orig-time <replaceable>timestamp</replaceable></option> (ICMP Originate Timestamp)
          <indexterm significance="preferred"><primary><option>--icmp-orig-time</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option sets the Originate Timestamp in ICMP Timestamp messages.
           The Originate Timestamp is expressed as the number of milliseconds
           since midnight UTC and it corresponds to the time the sender
           last touched the Timestamp message before its transmission. 
           <replaceable>timestamp</replaceable> can be specified as a regular
           time (e.g. <literal>10s</literal>, <literal>3h</literal>, <literal>1000ms</literal>), or the special string
           <literal>now</literal>. You can add or subtract
           values from <literal>now</literal>, for example
           <option>--icmp-orig-time now-2s</option>,
           <option>--icmp-orig-time now+1h</option>,
           <option>--icmp-orig-time now+200ms</option>.           
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>          
          <option>--icmp-recv-time <replaceable>timestamp</replaceable></option> (ICMP Receive Timestamp)
          <indexterm significance="preferred"><primary><option>--icmp-recv-time</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option sets the Receive Timestamp in ICMP Timestamp messages.
           The Receive Timestamp is expressed as the number of milliseconds
           since midnight UTC and it corresponds to the time the echoer
           first touched the Timestamp message on receipt.
           <replaceable>timestamp</replaceable> is as with
           <option>--icmp-orig-time</option>.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>          
          <option>--icmp-trans-time <replaceable>timestamp</replaceable></option> (ICMP Transmit Timestamp)
          <indexterm significance="preferred"><primary><option>--icmp-trans-time</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option sets the Transmit Timestamp in ICMP Timestamp messages.
           The Transmit Timestamp is expressed as the number of milliseconds
           since midnight UTC and it corresponds to the time the echoer
           last touched the Timestamp message before its transmission.
           <replaceable>timestamp</replaceable> is as with
           <option>--icmp-orig-time</option>.
        </para>
        </listitem>
      </varlistentry>

    </variablelist>

    <refsect2 id="nping-man-icmp-types">
      <indexterm class="startofrange" id="nping-man-icmp-types-indexterm"><primary>ICMP types</primary><secondary>mnemonics of, in Nping</secondary></indexterm>
      <title>ICMP Types</title>
  
      <para>
      These identifiers may be used as mnemonics for the ICMP type numbers given
      to the
      <option>--icmp-type</option><indexterm><primary><option>--icmp-type</option> (Nping option)</primary></indexterm>
      option. In general there are three forms of each identifier: the full name
      (e.g. <literal>destination-unreachable</literal>), the short name (e.g.
      <literal>dest-unr</literal>), or the initials (e.g. <literal>du</literal>).
      In ICMP types that request something, the word "request" is omitted.
      </para>

      <variablelist>
        <varlistentry>
          <term><literal>echo-reply</literal></term>
          <term><literal>echo-rep</literal></term>
          <term><literal>er</literal></term>
          <listitem>
            <para>
            Echo Reply (type 0). This message is sent in response to an Echo
            Request message.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>destination-unreachable</literal></term>
          <term><literal>dest-unr</literal></term>
          <term><literal>du</literal></term>
          <listitem>
            <para>
            Destination Unreachable (type 3). This message indicates that
            a datagram could not be delivered to its destination.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>source-quench</literal></term>
          <term><literal>sour-que</literal></term>
          <term><literal>sq</literal></term>
          <listitem>
            <para>
            Source Quench (type 4). This message is used by a congested
            IP device to tell other device that is sending packets too fast
            and that it should slow down.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>redirect</literal></term>
          <term><literal>redi</literal></term>
          <term><literal>r</literal></term>
          <listitem>
            <para>
            Redirect (type 5). This message is normally used by routers
            to inform a host that there is a better route to use for sending 
            datagrams. See also the <option>--icmp-redirect-addr</option>
            option.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>echo-request</literal></term>
          <term><literal>echo</literal></term>
          <term><literal>e</literal></term>
          <listitem>
            <para>
            Echo Request (type 8). This message is used to test the 
            connectivity of another device on a network.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>router-advertisement</literal></term>
          <term><literal>rout-adv</literal></term>
          <term><literal>ra</literal></term>
          <listitem>
            <para>
            Router Advertisement (type 9). This message is used by 
            routers to let hosts know of their existence and capabilities. See
            also the <option>--icmp-advert-lifetime</option> option.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>router-solicitation</literal></term>
          <term><literal>rout-sol</literal></term>
          <term><literal>rs</literal></term>
          <listitem>
            <para>
            Router Solicitation (type 10). This message is used by hosts 
            to request Router Advertisement messages from any listening 
            routers.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>time-exceeded</literal></term>
          <term><literal>time-exc</literal></term>
          <term><literal>te</literal></term>
          <listitem>
            <para>
            Time Exceeded (type 11). This message is generated by some
            intermediate device (normally a router) to indicate that a datagram 
            has been discarded before reaching its destination because the 
            IP TTL expired. 
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>parameter-problem</literal></term>
          <term><literal>member-pro</literal></term>
          <term><literal>pp</literal></term>
          <listitem>
            <para>
            Parameter Problem (type 12). This message is used when a device
            finds a problem with a parameter in an IP header and it cannot 
            continue processing it. See also the
            <option>--icmp-param-pointer</option> option.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>timestamp</literal></term>
          <term><literal>time</literal></term>
          <term><literal>tm</literal></term>
          <listitem>
            <para>
            Timestamp Request (type 13). This message is used to request
            a device to send a timestamp value for propagation time 
            calculation and clock synchronization. See also the
            <option>--icmp-orig-time</option>,
            <option>--icmp-recv-time</option>, and
            <option>--icmp-trans-time</option>.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>timestamp-reply</literal></term>
          <term><literal>time-rep</literal></term>
          <term><literal>tr</literal></term>
          <listitem>
            <para>
            Timestamp Reply (type 14). This message is sent in response 
            to a Timestamp Request message.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>information</literal></term>
          <term><literal>info</literal></term>
          <term><literal>i</literal></term>
          <listitem>
            <para>
            Information Request (type 15). This message is now obsolete
            but it was originally used to request configuration information
            from another device.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>information-reply</literal></term>
          <term><literal>info-rep</literal></term>
          <term><literal>ir</literal></term>
          <listitem>
            <para>
            Information Reply (type 16). This message is now obsolete but 
            it was originally sent in response to an Information Request 
            message to provide configuration information.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>mask-request</literal></term>
          <term><literal>mask</literal></term>
          <term><literal>m</literal></term>
          <listitem>
            <para>
            Address Mask Request (type 17). This message is used to
            ask a device to send its subnet mask.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>mask-reply</literal></term>
          <term><literal>mask-rep</literal></term>
          <term><literal>mr</literal></term>
          <listitem>
            <para>
            Address Mask Reply (type 18). This message contains a subnet 
            mask and is sent in response to a Address Mask Request message.
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>traceroute</literal></term>
          <term><literal>trace</literal></term>
          <term><literal>tc</literal></term>
          <listitem>
            <para>
            Traceroute (type 30). This message is normally sent 
            by an intermediate device when it receives an IP datagram
            with a traceroute option. ICMP Traceroute messages are still 
            experimental, see
            RFC 1393<indexterm><primary>RFC 1393</primary></indexterm>
            for more information. 
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
  
      <indexterm class="endofrange" startref="nping-man-icmp-types-indexterm"/>
    </refsect2>

    <refsect2 id="nping-man-icmp-codes">
      <indexterm class="startofrange" id="nping-man-icmp-codes-indexterm"><primary>ICMP codes</primary><secondary>mnemonics of, in Nping</secondary></indexterm>
      <title>ICMP Codes</title>
  
      <para>
      These identifiers may be used as mnemonics for the ICMP code numbers given
      to the
      <option>--icmp-code</option><indexterm><primary><option>--icmp-code</option> (Nping option)</primary></indexterm>
      option. They are listed by the ICMP type they correspond to.
      </para>

      <refsect3>
        <title>Destination Unreachable</title>

        <variablelist>
          <varlistentry>
            <term><literal>network-unreachable</literal></term>
            <term><literal>netw-unr</literal></term>
            <term><literal>net</literal></term>
            <listitem>
              <para>
              Code 0. Datagram could not be delivered to its destination
              network (probably due to some routing problem).
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>host-unreachable</literal></term>
            <term><literal>host-unr</literal></term>
            <term><literal>host</literal></term>
            <listitem>
              <para>
              Code 1. Datagram was delivered to the destination network but it
              was impossible to reach the specified host (probably due to some
              routing problem).
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>protocol-unreachable</literal></term>
            <term><literal>prot-unr</literal></term>
            <term><literal>proto</literal></term>
            <listitem>
              <para>
              Code 2. The protocol specified in the Protocol field of the IP
              datagram is not supported by the host to which the datagram was
              delivered.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>port-unreachable</literal></term>
            <term><literal>port-unr</literal></term>
            <term><literal>port</literal></term>
            <listitem>
              <para>
              Code 3. The TCP/UDP destination port was invalid.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>needs-fragmentation</literal></term>
            <term><literal>need-fra</literal></term>
            <term><literal>frag</literal></term>
            <listitem>
              <para>
              Code 4. Datagram had the DF bit set but it was too large for the
              MTU of the next physical network so it had to be dropped.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>source-route-failed</literal></term>
            <term><literal>sour-rou</literal></term>
            <term><literal>routefail</literal></term>
            <listitem>
              <para>
              Code 5. IP datagram had a Source Route option but a router
              couldn't pass it to the next hop.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>network-unknown</literal></term>
            <term><literal>netw-unk</literal></term>
            <term><literal>net?</literal></term>
            <listitem>
              <para>
              Code 6. Destination network is unknown. This code is never used.
              Instead, Network Unreachable is used.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>host-unknown</literal></term>
            <term><literal>host-unk</literal></term>
            <term><literal>host?</literal></term>
            <listitem>
              <para>
              Code 7. Specified host is unknown. Usually generated by a router
              local to the destination host to inform of a bad address.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>host-isolated</literal></term>
            <term><literal>host-iso</literal></term>
            <term><literal>isolated</literal></term>
            <listitem>
              <para>
              Code 8. Source Host Isolated. Not used.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>network-prohibited</literal></term>
            <term><literal>netw-pro</literal></term>
            <term><literal>!net</literal></term>
            <listitem>
              <para>
              Code 9. Communication with destination network is
              administratively prohibited (source device is not allowed to send
              packets to the destination network).
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>host-prohibited</literal></term>
            <term><literal>host-pro</literal></term>
            <term><literal>!host</literal></term>
            <listitem>
              <para>
              Code 10. Communication with destination host is administratively
              prohibited. (The source device is allowed to send packets to the
              destination network but not to the destination device.)
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>network-tos</literal></term>
            <term><literal>unreachable-network-tos</literal></term>
            <term><literal>netw-tos</literal></term>
            <term><literal>tosnet</literal></term>
            <listitem>
              <para>
              Code 11. Destination network unreachable because it cannot
              provide the type of service specified in the IP TOS field.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>host-tos</literal></term>
            <term><literal>unreachable-host-tos</literal></term>
            <term><literal>toshost</literal></term>
            <listitem>
              <para>
              Code 12. Destination host unreachable because it cannot provide
              the type of service specified in the IP TOS field.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>communication-prohibited</literal></term>
            <term><literal>comm-pro</literal></term>
            <term><literal>!comm</literal></term>
            <listitem>
              <para>
              Code 13. Datagram could not be forwarded due to filtering that
              blocks the message based on its contents.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>host-precedence-violation</literal></term>
            <term><literal>precedence-violation</literal></term>
            <term><literal>prec-vio</literal></term>
            <term><literal>violation</literal></term>
            <listitem>
              <para>
              Code 14. Precedence value in the IP TOS field is not permitted.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>precedence-cutoff</literal></term>
            <term><literal>prec-cut</literal></term>
            <term><literal>cutoff</literal></term>
            <listitem>
              <para>
              Code 15. Precedence value in the IP TOS field is lower than the
              minimum allowed for the network.
              </para>
            </listitem>
          </varlistentry>
        </variablelist>
      </refsect3>

      <refsect3>
        <title>Redirect</title>

        <variablelist>
          <varlistentry>
            <term><literal>redirect-network</literal></term>
            <term><literal>redi-net</literal></term>
            <term><literal>net</literal></term>
            <listitem>
              <para>
              Code 0. Redirect all future datagrams with the same destination
              network as the original datagram, to the router specified in the
              Address field. The use of this code is prohibited by
              RFC 1812.<indexterm><primary>RFC 1812</primary></indexterm>
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>redirect-host</literal></term>
            <term><literal>redi-host</literal></term>
            <term><literal>host</literal></term>
            <listitem>
              <para>
              Code 1. Redirect all future datagrams with the same destination
              host as the original datagram, to the router specified in the
              Address field.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>redirect-network-tos</literal></term>
            <term><literal>redi-ntos</literal></term>
            <term><literal>redir-ntos</literal></term>
            <listitem>
              <para>
              Code 2. Redirect all future datagrams with the same destination
              network and IP TOS value as the original datagram, to the router
              specified in the Address field. The use of this code is
              prohibited by RFC 1812.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>redirect-host-tos</literal></term>
            <term><literal>redi-htos</literal></term>
            <term><literal>redir-htos</literal></term>
            <listitem>
              <para>
              Code 3. Redirect all future datagrams with the same destination
              host and IP TOS value as the original datagram, to the router
              specified in the Address field.
              </para>
            </listitem>
          </varlistentry>
        </variablelist>
      </refsect3>

      <refsect3>
        <title>Router Advertisement</title>

        <variablelist>
          <varlistentry>
            <term><literal>normal-advertisement</literal></term>
            <term><literal>norm-adv</literal></term>
            <term><literal>normal</literal></term>
            <term><literal>zero</literal></term>
            <term><literal>default</literal></term>
            <term><literal>def</literal></term>
            <listitem>
              <para>
              Code 0. Normal router advertisement. In Mobile IP: Mobility agent
              can act as a router for IP datagrams not related to mobile nodes.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>not-route-common-traffic</literal></term>
            <term><literal>not-rou</literal></term>
            <term><literal>mobile-ip</literal></term>
            <term><literal>!route</literal></term>
            <term><literal>!commontraffic</literal></term>
            <listitem>
              <para>
              Code 16. Used for Mobile IP. The mobility agent does not route
              common traffic. All foreign agents must forward to a default
              router any datagrams received from a registered mobile node
              </para>
            </listitem>
          </varlistentry>
        </variablelist>
      </refsect3>

      <refsect3>
        <title>Time Exceeded</title>

        <variablelist>
          <varlistentry>
            <term><literal>ttl-exceeded-in-transit</literal></term>
            <term><literal>ttl-exc</literal></term>
            <term><literal>ttl-transit</literal></term>
            <listitem>
              <para>
              Code 0. IP Time To Live expired during transit.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>fragment-reassembly-time-exceeded</literal></term>
            <term><literal>frag-exc</literal></term>
            <term><literal>frag-time</literal></term>
            <listitem>
              <para>
              Code 1. Fragment reassembly time has been exceeded.
              </para>
            </listitem>
          </varlistentry>
        </variablelist>
      </refsect3>

      <refsect3>
        <title>Parameter Problem</title>

        <variablelist>
          <varlistentry>
            <term><literal>pointer-indicates-error</literal></term>
            <term><literal>poin-ind</literal></term>
            <term><literal>pointer</literal></term>
            <listitem>
              <para>
              Code 0. The pointer field indicates the location of the problem.
              See the <option>--icmp-param-pointer</option> option.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>missing-required-option</literal></term>
            <term><literal>miss-option</literal></term>
            <term><literal>option-missing</literal></term>
            <listitem>
              <para>
              Code 1. IP datagram was expected to have an option that is not
              present.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>bad-length</literal></term>
            <term><literal>bad-len</literal></term>
            <term><literal>badlen</literal></term>
            <listitem>
              <para>
              Code 2. The length of the IP datagram is incorrect.
              </para>
            </listitem>
          </varlistentry>
        </variablelist>
      </refsect3>

<!--
      <refsect3>
        <title>ICMP Security Failures Messages (Experimental)</title>

        <variablelist>
          <varlistentry>
            <term><literal>bad-spi</literal></term>
            <term><literal>badspi</literal></term>
            <term><literal>!spi</literal></term>
            <listitem>
              <para>
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>authentication-failed</literal></term>
            <term><literal>auth-fai</literal></term>
            <term><literal>auth-failed</literal></term>
            <term><literal>authfail</literal></term>
            <term><literal>!auth</literal></term>
            <listitem>
              <para>
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>decompression-failed</literal></term>
            <term><literal>deco-fai</literal></term>
            <term><literal>decom-failed</literal></term>
            <term><literal>!decompress</literal></term>
            <term><literal>!decompression</literal></term>
            <listitem>
              <para>
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>decryption-failed</literal></term>
            <term><literal>decr-fai</literal></term>
            <term><literal>decrypt-failed</literal></term>
            <term><literal>!decrypt</literal></term>
            <term><literal>!decryption</literal></term>
            <listitem>
              <para>
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>need-authentication</literal></term>
            <term><literal>need-aut</literal></term>
            <term><literal>need-auth</literal></term>
            <term><literal>auth-needed</literal></term>
            <term><literal>!auth</literal></term>
            <listitem>
              <para>
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>need-authorization</literal></term>
            <term><literal>need-author</literal></term>
            <term><literal>authorization-needed</literal></term>
            <term><literal>author-needed</literal></term>
            <term><literal>!author</literal></term>
            <term><literal>!authorization</literal></term>
            <listitem>
              <para>
              </para>
            </listitem>
          </varlistentry>
        </variablelist>
      </refsect3>
-->
  
      <indexterm class="endofrange" startref="nping-man-icmp-types-indexterm"/>
    </refsect2>
  </refsect1>

<!-- ARP MODE ************************************************************* -->
  <refsect1 id="nping-man-arp-mode">
  <title>ARP Mode</title>


    <variablelist>

      <varlistentry>
        <term>          
          <option>--arp-type <replaceable>type</replaceable></option> (ICMP Type)
          <indexterm significance="preferred"><primary><option>--arp-type</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option specifies which type of ARP messages should be
           generated. <replaceable>type</replaceable> can be supplied in
           two different ways. You can use the
           <ulink url="http://www.iana.org/assignments/arp-parameters/">official
           numbers assigned by IANA</ulink>
           (e.g. <option>--arp-type 1</option> for ARP Request), or you can use
           one of the mnemonics from <xref linkend="nping-man-arp-types"/>.
        </para>
       </listitem>
      </varlistentry>


      <varlistentry>
        <term>          
          <option>--arp-sender-mac <replaceable>mac</replaceable></option> (Sender MAC address)
          <indexterm significance="preferred"><primary><option>--arp-sender-mac</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
        <para>
           This option sets the Sender Hardware Address field of the ARP header.
           Although ARP supports many types of link layer addresses, currently
           Nping only supports MAC addresses. 
           <replaceable>mac</replaceable> must be specified using the
           traditional MAC notation (e.g. <literal>00:0a:8a:32:f4:ae</literal>). You can also use
           hyphens as separators (e.g. <literal>00-0a-8a-32-f4-ae</literal>).
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>          
          <option>--arp-sender-ip <replaceable>addr</replaceable></option> (Sender IP address)
          <indexterm significance="preferred"><primary><option>--arp-sender-ip</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
        <para>
           This option sets the Sender IP field of the ARP header.
           <replaceable>addr</replaceable> can be given as an IPv4 address or a
           hostname.
        </para>
        </listitem>
      </varlistentry>
              

      <varlistentry>
        <term>          
          <option>--arp-target-mac <replaceable>mac</replaceable></option> (target MAC address)
          <indexterm significance="preferred"><primary><option>--arp-target-mac</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
        <para>
           This option sets the Target Hardware Address field of the ARP header.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>          
          <option>--arp-target-ip <replaceable>addr</replaceable></option> (target ip address)
          <indexterm significance="preferred"><primary><option>--arp-target-ip</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
        <para>
           This option sets the Target IP field of the ARP header.
        </para>
        </listitem>
      </varlistentry>

    </variablelist>

    <refsect2 id="nping-man-arp-types">
      <indexterm class="startofrange" id="nping-man-arp-types-indexterm"><primary>ARP types</primary><secondary>mnemonics of, in Nping</secondary></indexterm>
      <title>ARP Types</title>

      <para>
      These identifiers may be used as mnemonics for the ARP type numbers given
      to the
      <option>--arp-type</option><indexterm><primary><option>--arp-type</option> (Nping option)</primary></indexterm>
      option.
      </para>

      <variablelist>
          <varlistentry>
            <term><literal>arp-request</literal></term>
            <term><literal>arp</literal></term>
            <term><literal>a</literal></term>
            <listitem>
              <para>
              ARP Request (type 1). ARP requests are used to translate network
              layer addresses (normally IP addresses) to link layer addresses
              (usually MAC addresses). Basically, and ARP request is a
              broadcasted message that asks the host in the same network
              segment that has a given IP address to provide its MAC address.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>arp-reply</literal></term>
            <term><literal>arp-rep</literal></term>
            <term><literal>ar</literal></term>
            <listitem>
              <para>
              ARP Reply (type 2). An ARP reply is a message that a host sends in
              response to an ARP request to provide its link layer address.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>rarp-request</literal></term>
            <term><literal>rarp</literal></term>
            <term><literal>r</literal></term>
            <listitem>
              <para>
              RARP Requests (type 3). RARP requests are used to translate a
              link layer address (normally a MAC address) to a network layer
              address (usually an IP address). Basically a RARP request is a
              broadcasted message sent by a host that wants to know his own IP
              address because it doesn't have any. It was the first protocol
              designed to solve the bootstrapping problem. However, RARP is now
              obsolete and DHCP is used instead. For more information about
              RARP see
              RFC 903.<indexterm><primary>RFC 903</primary></indexterm>
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>rarp-reply</literal></term>
            <term><literal>rarp-rep</literal></term>
            <term><literal>rr</literal></term>
            <listitem>
              <para>
              RARP Reply (type 4). A RARP reply is a message sent in response
              to a RARP request to provide an IP address to the host that sent
              the RARP request in the first place.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>drarp-request</literal></term>
            <term><literal>drarp</literal></term>
            <term><literal>d</literal></term>
            <listitem>
              <para>
              Dynamic RARP Request (type 5). Dynamic RARP is an extension to
              RARP used to obtain or assign a network layer address from a
              fixed link layer address. DRARP was used mainly in Sun
              Microsystems platforms in the late 90's but now it's no longer
              used. See
              RFC 1931<indexterm><primary>RFC 1931</primary></indexterm>
              for more information.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>drarp-reply</literal></term>
            <term><literal>drarp-rep</literal></term>
            <term><literal>dr</literal></term>
            <listitem>
              <para>
              Dynamic RARP Reply (type 6). A DRARP reply is a message sent in
              response to a RARP request to provide network layer address.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>drarp-error</literal></term>
            <term><literal>drarp-err</literal></term>
            <term><literal>de</literal></term>
            <listitem>
              <para>
              DRARP Error (type 7). DRARP Error messages are usually sent in
              response to DRARP requests to inform of some error. In DRARP
              Error messages, the Target Protocol Address field is used to
              carry an error code (usually in the first byte). The error code
              is intended to tell why no target protocol address is being
              returned. For more information see RFC 1931.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>inarp-request</literal></term>
            <term><literal>inarp</literal></term>
            <term><literal>i</literal></term>
            <listitem>
              <para>
              Inverse ARP Request (type 8). InARP requests are used to
              translate a link layer address to a network layer address. It is
              similar to RARP request but in this case, the sender of the InARP
              request wants to know the network layer address of another node,
              not its own address. InARP is mainly used in Frame Relay and ATM
              networks. For more information see
              RFC 2390.<indexterm><primary>RFC 2390</primary></indexterm>
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>inarp-reply</literal></term>
            <term><literal>inarp-rep</literal></term>
            <term><literal>ir</literal></term>
            <listitem>
              <para>
              Inverse ARP Reply (type 9). InARP reply messages are sent in
              response to InARP requests to provide the network layer address
              associated with the host that has a given link layer address.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>arp-nak</literal></term>
            <term><literal>an</literal></term>
            <listitem>
              <para>
              ARP NAK (type 10). ARP NAK messages are an extension to the
              ATMARP protocol and they are used to improve the robustness of
              the ATMARP server mechanism. With ARP NAK, a client can determine
              the difference between a catastrophic server failure and an
              ATMARP table lookup failure. See
              RFC 1577<indexterm><primary>RFC 1577</primary></indexterm>
              for more information.
              </para>
            </listitem>
          </varlistentry>
        </variablelist>

      <indexterm class="endofrange" startref="nping-man-arp-types-indexterm"/>
    </refsect2>

  </refsect1>



<!-- IPv4 OPTIONS ********************************************************** -->
  <refsect1 id="nping-man-ip-options">
  <title>IPv4 Options</title>

  <variablelist>

      <varlistentry>
        <term>
          <option>-S <replaceable>addr</replaceable></option>,
          <option>--source-ip <replaceable>addr</replaceable></option> (Source IP Address)
          <indexterm significance="preferred"><primary><option>--source-ip</option> (Nping option)</primary></indexterm>
          <indexterm significance="preferred"><primary><option>-S</option> (Nping option)</primary><see><option>--source-ip</option></see></indexterm>
        </term>
        <listitem>
          <para>
           Sets the source IP address. This option lets you specify a custom IP
           address to be used as source IP address in sent packets. This
           allows spoofing the sender of the packets.
           <replaceable>addr</replaceable> can be an IPv4 address or a hostname.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <option>--dest-ip <replaceable>addr</replaceable></option> (Destination IP Address)
          <indexterm significance="preferred"><primary><option>--dest-ip</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           Adds a target to Nping's target list.
           This option is provided for consistency but its use is deprecated
           in favor of plain target specifications. See
           <xref linkend="nping-man-target-specification"/>.
        </para>
        </listitem>
      </varlistentry>      

       <varlistentry>
        <term>          
          <option>--tos <replaceable>tos</replaceable></option> (Type of Service)
          <indexterm significance="preferred"><primary><option>--tos</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           Sets the IP TOS field. The TOS field is used to carry information
           to provide quality of service features. It is normally used to
           support a technique called Differentiated Services. See
           RFC 2474<indexterm><primary>RFC 2474</primary></indexterm>
           for
           more information. <replaceable>tos</replaceable> must be a number
           in the range [0&ndash;255].
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>          
          <option>--id <replaceable>id</replaceable></option> (Identification)
          <indexterm significance="preferred"><primary><option>--id</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           Sets the IPv4 Identification field. The Identification field is a
           16-bit value that is common to all fragments belonging to a particular
           message. The value is used by the receiver to reassemble the
           original message from the fragments received. <replaceable>id</replaceable>
           must be a number in the range [0&ndash;65535].
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>          
          <option>--df</option> (Don't Fragment)
          <indexterm significance="preferred"><primary><option>--df</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           Sets the Don't Fragment bit in sent packets. When an
           IP datagram has its DF flag set, intermediate devices are not
           allowed to fragment it so if it needs to travel across a network
           with a MTU smaller that datagram length the datagram will have
           to be dropped. Normally an ICMP Destination Unreachable message
           is generated and sent back to the sender. 
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>          
          <option>--mf</option> (More Fragments)
          <indexterm significance="preferred"><primary><option>--mf</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           Sets the More Fragments bit in sent packets. The MF
           flag is set to indicate the receiver that the current datagram is
           a fragment of some larger datagram. When set to zero it indicates
           that the current datagram is either the last fragment in the set
           or that it is the only fragment.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <option>--evil</option> (Reserved / Evil)
          <indexterm significance="preferred"><primary><option>--evil</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           Sets the Reserved / Evil bit in sent packets. The Evil flag
           helps firewalls and other network security systems to distinguish
           between datagrams that have malicious intent and those that are
           merely unusual. When set, it indicates that the datagram has evil
           intent, instructing insecure systems to succumb. Setting it to zero
           indicates no evil intent. The option is implied if environmental
           variable SCRIPT_KIDDIE is set to a non-zero value.
        </para>
        </listitem>
      </varlistentry>

       <varlistentry>
        <term>          
          <option>--ttl <replaceable>hops</replaceable></option> (Time To Live)
          <indexterm significance="preferred"><primary><option>--ttl</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           Sets the IPv4 Time-To-Live (TTL) field in sent packets to the given
           value. The TTL field specifies how long the datagram is allowed
           to exist on the network. It was originally intended to represent
           a number of seconds but it actually represents the number of
           hops a packet can traverse before being dropped. The TTL tries to
           avoid a situation in which undeliverable datagrams keep being
           forwarded from one router to another endlessly.
           <replaceable>hops</replaceable> must be a number in the range [0&ndash;255].
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>          
          <option>--badsum-ip</option> (Invalid IP checksum)
          <indexterm significance="preferred"><primary><option>--badsum-ip</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           Asks Nping to use an invalid IP checksum for packets sent to 
           target hosts. Note that some systems (like most Linux kernels),
           may fix the checksum before placing the packet on the wire, so
           even if Nping shows the incorrect checksum in its output, the
           packets may be transparently corrected by the kernel.
        </para>
        </listitem>
      </varlistentry>

      
      <varlistentry>
        <term>          
          <option>--ip-options <replaceable>R|S [route]|L [route]|T|U ...</replaceable></option>,
          <option>--ip-options <replaceable>hex string</replaceable></option>  (IP Options)
          <indexterm significance="preferred"><primary><option>--ip-options</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           The IP protocol offers several options which may be placed in
           packet headers. Unlike the ubiquitous TCP options, IP options are
           rarely seen due to practicality and security concerns. In fact,
           many Internet routers block the most dangerous options such as
           source routing. Yet options can still be useful in some cases for
           determining and manipulating the network route to target machines.
           For example, you may be able to use the record route option to
           determine a path to a target even when more traditional
           traceroute-style approaches fail. Or if your packets are being
           dropped by a certain firewall, you may be able to specify a
           different route with the strict or loose source routing options.
          </para>

          <para>
           The most powerful way to specify IP options is to simply pass in hexadecimal data
           as the argument to <option>--ip-options</option>. Precede each hex byte value
           with <literal>\x</literal>. You may repeat certain characters by
           following them with an asterisk and then the number of times you
           wish them to repeat. For example,
           <literal>\x01\x07\x04\x00*4</literal> is the same as
           <literal>\x01\x07\x04\x00\x00\x00\x00</literal>.
          </para>

          <para>
           Note that if you specify a number of bytes that is not a multiple
           of four, an incorrect IP header length will be set in the IP
           packet. The reason for this is that the IP header length field
           can only express multiples of four. In those cases, the length is
           computed by dividing the header length by 4 and rounding down.
           This will
           affect the way the header that follows the IP header is
           interpreted, showing bogus information in Nping or in the output
           of any sniffer. Although this kind of situation might be useful
           for some stack stress tests, users would normally want to
           specify explicit padding, so the correct header length is set.
          </para>

          <para>
           Nping also offers a shortcut mechanism for specifying options.
           Simply pass the letter <literal>R</literal>, <literal>T</literal>, or <literal>U</literal> to request record-route,
           record-timestamp, or both options together, respectively. Loose
           or strict source routing may be specified with an L or S followed
           by a space and then a space-separated list of IP addresses.
          </para>

          <para>
           For more information and examples of using IP options with Nping,
           see the mailing list post at
           <ulink url="https://seclists.org/nmap-dev/2006/q3/0052.html"/>.
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>          
          <option>--mtu <replaceable>size</replaceable></option> (Maximum Transmission Unit)
          <indexterm significance="preferred"><primary><option>--mtu</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option sets a fictional MTU in Nping so IP datagrams larger than
           <replaceable>size</replaceable> are fragmented before transmission.
           <replaceable>size</replaceable> must be specified in bytes and
           corresponds to the number of octets that can be carried on a
           single link-layer frame.
        </para>
        </listitem>
      </varlistentry>      
      

    </variablelist>
  </refsect1>





<!-- IPv6 OPTIONS ********************************************************** -->
 <refsect1 id="nping-man-ip6-options">
  <title>IPv6 Options</title>

  <variablelist>

      <varlistentry>
        <term>
          <option>-6</option>,
          <option>--ipv6</option> (Use IPv6)
          <indexterm significance="preferred"><primary><option>--ipv6</option> (Nping option)</primary></indexterm>
          <indexterm significance="preferred"><primary><option>-6</option> (Nping option)</primary><see><option>--ipv6</option></see></indexterm>
        </term>
        <listitem>
          <para>
           Tells Nping to use IP version 6 instead of the default IPv4.
           It is generally a good idea to specify this option as early as
           possible in the command line so Nping can parse it soon and know in
           advance that the rest of the parameters refer to IPv6. The command
           syntax is the same as usual except that you also add the <option>-6</option> option.
           Of course, you must use IPv6 syntax if you specify an address
           rather than a hostname. An address might look like
           <option>3ffe:7501:4819:2000:210:f3ff:fe03:14d0</option>, so hostnames are
           recommended. 
        </para>
        <para>
           While IPv6 hasn't exactly taken the world by storm, it gets
           significant use in some (usually Asian) countries and most modern
           operating systems support it. To use Nping with IPv6, both the
           source and target of your packets must be configured for IPv6. If your
           ISP (like most of them) does not allocate IPv6 addresses to you,
           free tunnel brokers are widely available and work fine with Nping.
           You can use the free IPv6 tunnel broker service at
           <ulink url="http://www.tunnelbroker.net"/>.
        </para>
        <para>
           Please note that IPv6 support is still highly experimental and
           many modes and options may not work with it.
        </para>

        </listitem>
      </varlistentry>


      
      <varlistentry>
        <term>
          <option>-S <replaceable>addr</replaceable></option>,
          <option>--source-ip <replaceable>addr</replaceable></option> (Source IP Address)
          <indexterm significance="preferred"><primary><option>--source-ip</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           Sets the source IP address. This option lets you specify a custom IP
           address to be used as source IP address in sent packets. This
           allows spoofing the sender of the packets.
           <replaceable>addr</replaceable> can be an IPv6 address or a hostname.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <option>--dest-ip <replaceable>addr</replaceable></option> (Destination IP Address)
          <indexterm significance="preferred"><primary><option>--dest-ip</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           Adds a target to Nping's target list.
           This option is provided for consistency but its use is deprecated
           in favor of plain target specifications. See
           <xref linkend="nping-man-target-specification"/>.
        </para>
        </listitem>
      </varlistentry>      


       <varlistentry>
        <term>          
          <option>--flow <replaceable>label</replaceable></option> (Flow Label)
          <indexterm significance="preferred"><primary><option>--flow</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
            Sets the IPv6 Flow Label. The Flow Label field is 20 bits long and is
            intended to provide certain quality-of-service properties for
            real-time datagram delivery. However, it has not been widely
            adopted, and not all routers or endpoints support it. Check
            RFC 2460<indexterm><primary>RFC 2560</primary></indexterm>
            for more information. <replaceable>label</replaceable> must be an
            integer in the range [0&ndash;1048575].
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>          
          <option>--traffic-class <replaceable>class</replaceable></option> (Traffic Class)
          <indexterm significance="preferred"><primary><option>--traffic-class</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
          Sets the IPv6 Traffic Class. This field is similar to the TOS field in
          IPv4, and is intended to provide the Differentiated Services
          method, enabling scalable service discrimination in the Internet
          without the need for per-flow state and signaling at every hop. Check
          RFC 2474<indexterm><primary>RFC 2474</primary></indexterm>
          for more information. <replaceable>class</replaceable> must
          be an integer in the range [0&ndash;255].
        </para>
        </listitem>
      </varlistentry>


       <varlistentry>
        <term>          
          <option>--hop-limit <replaceable>hops</replaceable></option> (Hop Limit)
          <indexterm significance="preferred"><primary><option>--hop-limit</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           <indexterm><primary>hop limit (IPv6)</primary><seealso>TTL</seealso></indexterm>
           Sets the IPv6 Hop Limit field in sent packets to the given
           value. The Hop Limit field specifies how long the datagram is allowed
           to exist on the network. It represents the number of hops a packet
           can traverse before being dropped. As with the TTL in IPv4, IPv6 Hop Limit
           tries to avoid a situation in which undeliverable datagrams keep being
           forwarded from one router to another endlessly.
           <replaceable>hops</replaceable> must be a number in the range [0&ndash;255].
        </para>
        </listitem>
      </varlistentry>
     

    </variablelist>
  </refsect1>






<!-- ETHERNET OPTIONS ***************************************************** -->
 <refsect1 id="nping-man-ethernet-options">
  <title>Ethernet Options</title>

   <para>
    In most cases Nping sends packets at the raw IP level. This means that Nping
    creates its own IP packets and transmits them through a raw socket. However,
    in some cases it may be necessary to send packets at the raw Ethernet level.
    This happens, for example, when Nping is run under Windows (as Microsoft
    has disabled raw socket support since Windows XP SP2), or when Nping is
    asked to send ARP packets.
    Since in some cases it is necessary to construct ethernet frames, Nping
    offers some options to manipulate the different fields.
   </para>

  <variablelist>

      <varlistentry>
        <term>          
          <option>--dest-mac <replaceable>mac</replaceable></option> (Ethernet Destination MAC Address)
          <indexterm significance="preferred"><primary><option>--dest-mac</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option sets the destination MAC address that should be set in
           outgoing Ethernet frames. This is useful in case Nping can't
           determine the next hop's MAC address or when you want to route
           probes through a router other than the configured default
           gateway. The MAC address should have the usual format of
           six colon-separated bytes, e.g. <literal>00:50:56:d4:01:98</literal>.
           Alternatively, hyphens may be used instead of colons.
           Use the word <literal>random</literal> or <literal>rand</literal> to
           generate a random address, and <literal>broadcast</literal> or
           <literal>bcast</literal> to use ff:ff:ff:ff:ff:ff.
           If you set up a bogus destination MAC address your probes may not
           reach the intended targets.
          </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>          
          <option>--source-mac <replaceable>mac</replaceable></option> (Ethernet Source MAC Address)
          <indexterm significance="preferred"><primary><option>--source-mac</option> (Nping option)</primary></indexterm>
        </term>        
        <listitem>
          <para> 
           This option sets the source MAC address that should be set in
           outgoing Ethernet frames. This is useful in case Nping can't
           determine your network interface MAC address or when you want to
           inject traffic into the network while hiding your network card's real
           address. The syntax is the same as for <literal>--dest-mac</literal>.
           If you set up a bogus source MAC address
           you may not receive probe replies.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>          
          <option>--ether-type <replaceable>type</replaceable></option> (Ethertype)
          <indexterm significance="preferred"><primary><option>--ether-type</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option sets the Ethertype field of the ethernet frame.
           The Ethertype is used to indicate which protocol is encapsulated
           in the payload. <replaceable>type</replaceable> can be supplied in
           two different ways. You can use the
           <ulink url="http://standards.ieee.org/regauth/ethertype/eth.txt">official
           numbers listed by the IEEE</ulink>
           (e.g. <option>--ether-type 0x0800</option> for IP version 4),
           or one of the mnemonics from
           <xref linkend="nping-man-ether-types" xrefstyle="template:the section called &#x201c;%t&#x201d;"/>.
           <!-- Hide the page number, but also include the section title. xrefstyle="select: label nopage" doesn't work here. -->
        </para>
        
        </listitem>
      </varlistentry>          

    </variablelist>

    <refsect2 id="nping-man-ether-types">
      <indexterm class="startofrange" id="nping-man-arp-ether-indexterm"><primary>Ethernet types</primary><secondary>mnemonics of, in Nping</secondary></indexterm>
      <title>Ethernet Types</title>

      <para>
      These identifiers may be used as mnemonics for the Ethertype numbers given
      to the
      <option>--arp-type</option><indexterm><primary><option>--arp-type</option> (Nping option)</primary></indexterm>
      option.
      </para>

      <variablelist>
        <varlistentry>
          <term><literal>ipv4</literal></term>
          <term><literal>ip</literal></term>
          <term><literal>4</literal></term>
          <listitem>
            <para>
            Internet Protocol version 4 (type 0x0800).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>ipv6</literal></term>
          <term><literal>6</literal></term>
          <listitem>
            <para>
            Internet Protocol version 6 (type 0x86DD).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>arp</literal></term>
          <listitem>
            <para>
            Address Resolution Protocol (type 0x0806).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>rarp</literal></term>
          <listitem>
            <para>
            Reverse Address Resolution Protocol (type 0x8035).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>frame-relay</literal></term>
          <term><literal>frelay</literal></term>
          <term><literal>fr</literal></term>
          <listitem>
            <para>
            Frame Relay (type 0x0808).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>ppp</literal></term>
          <listitem>
            <para>
            Point-to-Point Protocol (type 0x880B).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>gsmp</literal></term>
          <listitem>
            <para>
            General Switch Management Protocol (type 0x880C).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>mpls</literal></term>
          <listitem>
            <para>
            Multiprotocol Label Switching (type 0x8847).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>mps-ual</literal></term>
          <term><literal>mps</literal></term>
          <listitem>
            <para>
            Multiprotocol Label Switching with Upstream-assigned Label (type 0x8848).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>mcap</literal></term>
          <listitem>
            <para>
            Multicast Channel Allocation Protocol (type 0x8861).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>pppoe-discovery</literal></term>
          <term><literal>pppoe-d</literal></term>
          <listitem>
            <para>
            PPP over Ethernet Discovery Stage (type 0x8863).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>pppoe-session</literal></term>
          <term><literal>pppoe-s</literal></term>
          <listitem>
            <para>
            PPP over Ethernet Session Stage (type 0x8864).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>ctag</literal></term>
          <listitem>
            <para>
            Customer VLAN Tag Type (type 0x8100).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>epon</literal></term>
          <listitem>
            <para>
            Ethernet Passive Optical Network (type 0x8808).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>pbnac</literal></term>
          <listitem>
            <para>
            Port-based network access control (type 0x888E).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>stag</literal></term>
          <listitem>
            <para>
            Service VLAN tag identifier (type 0x88A8).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>ethexp1</literal></term>
          <listitem>
            <para>
            Local Experimental Ethertype 1 (type 0x88B5).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>ethexp2</literal></term>
          <listitem>
            <para>
            Local Experimental Ethertype 2 (type 0x88B6).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>ethoui</literal></term>
          <listitem>
            <para>
            OUI Extended Ethertype (type 0x88B7).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>preauth</literal></term>
          <listitem>
            <para>
            Pre-Authentication (type 0x88C7).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>lldp</literal></term>
          <listitem>
            <para>
            Link Layer Discovery Protocol (type 0x88CC).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>mac-security</literal></term>
          <term><literal>mac-sec</literal></term>
          <term><literal>macsec</literal></term>
          <listitem>
            <para>
            Media Access Control Security (type 0x88E5).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>mvrp</literal></term>
          <listitem>
            <para>
            Multiple VLAN Registration Protocol (type 0x88F5).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>mmrp</literal></term>
          <listitem>
            <para>
            Multiple Multicast Registration Protocol (type 0x88F6).
            </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term><literal>frrr</literal></term>
          <listitem>
            <para>
            Fast Roaming Remote Request (type 0x890D).
            </para>
          </listitem>
        </varlistentry>
      </variablelist>

      <indexterm class="endofrange" startref="nping-man-ether-types-indexterm"/>
    </refsect2>
  </refsect1>

  


<!-- PAYLOAD OPTIONS ******************************************************* -->
 <refsect1 id="nping-man-payload-options">
  <title>Payload Options</title>

  <variablelist>

      <varlistentry>
        <term>
           <option>--data <replaceable>hex string</replaceable></option> (Append custom binary data to sent packets)
          <indexterm significance="preferred"><primary><option>--data</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option lets you include binary data as payload in sent packets.
           <replaceable>hex string</replaceable> may be specified in any of
           the following formats: <literal>0xAABBCCDDEEFF<replaceable>...</replaceable></literal>,
           <literal>AABBCCDDEEFF<replaceable>...</replaceable></literal> or
           <literal>\xAA\xBB\xCC\xDD\xEE\xFF<replaceable>...</replaceable></literal>.
           Examples of use are <option>--data 0xdeadbeef</option> and
           <option>--data \xCA\xFE\x09</option>. Note that if you specify a
           number like <literal>0x00ff</literal>
           no byte-order conversion is performed. Make sure you specify
           the information in the byte order expected by the receiver.
        </para>
        </listitem>
      </varlistentry>

     
      <varlistentry>
        <term>
          <option>--data-string <replaceable>string</replaceable></option> (Append custom string to sent packets)
          <indexterm significance="preferred"><primary><option>--data-string</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
            This option lets you include a regular string as payload in
            sent packets. <replaceable>string</replaceable> can
            contain any string. However, note that some characters
            may depend on your system's locale and the receiver may not
            see the same information. Also, make sure you enclose the string
            in double quotes and escape any special characters from the shell.
            Example: <option>--data-string "Jimmy Jazz..."</option>.
        </para>
        </listitem>
      </varlistentry>

       <varlistentry>
        <term>          
          <option>--data-length <replaceable>len</replaceable></option> (Append random data to sent packets)
          <indexterm significance="preferred"><primary><option>--data-length</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option lets you include <replaceable>len</replaceable>
           random bytes of data as payload in sent packets.
           <replaceable>len</replaceable> must be an integer in the range
           [0&ndash;65400]. However, values higher than 1400 are not recommended
           because it may not be possible to transmit packets due to
           network MTU limitations.
        </para>
        </listitem>
      </varlistentry>
     

    </variablelist>
  </refsect1>
    





<!-- ECHO MODE ****************************************************** -->
  <refsect1 id="nping-man-echo-mode">
  <title>Echo Mode</title>

    <para>
    The "Echo Mode" is a novel technique implemented by Nping which lets users
    see how network packets change in transit, from the host where they
    originated to the target machine. Basically, the Echo mode turns Nping into
    two different pieces: the Echo server and the Echo client. The Echo server
    is a network service that has the ability to capture packets from the
    network and send a copy ("echo them") to the originating client through a
    side TCP channel. The Echo client is the part that generates such network
    packets, transmits them to the server, and receives their echoed version
    through a side TCP channel that it has previously established with the Echo
    server.
    </para>

    <para>
    This scheme lets the client see the differences between the packets that it
    sends and what is actually received by the server. By having the server
    send back copies of the received packets through the side channel, things
    like NAT devices become immediately apparent to the client because it
    notices the changes in the source IP address (and maybe even source
    port). Other devices like those that perform traffic shaping, changing
    TCP window sizes or adding TCP options transparently between hosts, turn up
    too. 
    </para>

    <para>
    The Echo mode is also useful for troubleshooting routing and firewall issues.
    Among other things, it can be used to determine if the traffic generated
    by the Nping client is being dropped in transit and never gets to its
    destination or if the responses are the ones that don't get back to it.
    </para>

    <para>
    Internally, client and server communicate over an encrypted and
    authenticated channel, using the Nping Echo Protocol (NEP), whose technical
    specification can be found in
    <ulink url="https://nmap.org/svn/nping/docs/EchoProtoRFC.txt"/> 
    </para>

    <para>
    The following paragraphs describe the different options available in Nping's
    Echo mode.
    </para>
    
    <variablelist>

      <varlistentry>
        <term>          
          <option>--ec <replaceable>passphrase</replaceable></option>,
          <option>--echo-client <replaceable>passphrase</replaceable></option> (Run Echo client)
          <indexterm significance="preferred"><primary><option>--echo-client</option> (Nping option)</primary></indexterm>
          <indexterm significance="preferred"><primary><option>--ec</option> (Nping option)</primary><see><option>--echo-client</option></see></indexterm>
        </term>
        <listitem>
        <para>
           This option tells Nping to run as an Echo client. 
           <replaceable>passphrase</replaceable> is a sequence of ASCII
           characters that is used used to generate the cryptographic
           keys needed for encryption and authentication in a given session.
           The passphrase should be a secret that is also known by the server, 
           and it may contain any number of printable ASCII characters.
           Passphrases that contain whitespace or special characters must be
           enclosed in double quotes.
        </para>

        <para>
           When running Nping as an Echo client, most options from the regular
           raw probe modes apply. The client may be configured to send specific
           probes using flags like <option>--tcp</option>,
           <option>--icmp</option> or <option>--udp</option>. Protocol header
           fields may be manipulated normally using the appropriate options
           (e.g. <option>--ttl</option>, <option>--seq</option>,
           <option>--icmp-type</option>, etc.). The only exceptions are
           ARP-related flags, which are not supported in Echo mode, as protocols
           like ARP are closely related to the data link layer and its probes
           can't pass through different network segments.
        </para>
        
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>          
          <option>--es <replaceable>passphrase</replaceable></option>,
          <option>--echo-server <replaceable>passphrase</replaceable></option> (Run Echo server)
          <indexterm significance="preferred"><primary><option>--echo-server</option> (Nping option)</primary></indexterm>
          <indexterm significance="preferred"><primary><option>--es</option> (Nping option)</primary><see><option>--echo-server</option></see></indexterm>
        </term>
        <listitem>
        <para>
           This option tells Nping to run as an Echo server.
           <replaceable>passphrase</replaceable> is a sequence of ASCII
           characters that is used used to generate the cryptographic
           keys needed for encryption and authentication in a given session.
           The passphrase should be a secret that is also known by the clients, 
           and it may contain any number of printable ASCII characters.
           Passphrases that contain whitespace or special characters must be
           enclosed in double quotes. Note that although it is not recommended,
           it is possible to use empty passphrases, supplying
           <option>--echo-server ""</option>. However, if what you
           want is to set up an open Echo server, it is better to use option 
           <option>--no-crypto</option>. See below for details. 
        </para>
        </listitem>
      </varlistentry>



      <varlistentry>
        <term>          
          <option>--ep <replaceable>port</replaceable></option>,
          <option>--echo-port <replaceable>port</replaceable></option> (Set Echo TCP port number)
          <indexterm significance="preferred"><primary><option>--echo-port</option> (Nping option)</primary></indexterm>
          <indexterm significance="preferred"><primary><option>--ep</option> (Nping option)</primary><see><option>--echo-port</option></see></indexterm>
        </term>
        <listitem>
        <para>
           This option asks Nping to use the specified TCP port number for the
           Echo side channel connection. If this option is used with
           <option>--echo-server</option>, it specifies the port on which the
           server listens for connections. If it is used with
           <option>--echo-client</option>, it specifies the port to connect to
           on the remote host. By default, port number 9929 is used.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <option>--nc</option>,
          <option>--no-crypto</option> (Disable encryption and authentication)
          <indexterm significance="preferred"><primary><option>--no-crypto</option> (Nping option)</primary></indexterm>
          <indexterm significance="preferred"><primary><option>--nc</option> (Nping option)</primary><see><option>--no-crypto</option></see></indexterm>
        </term>
        <listitem>
        <para>
           This option asks Nping not to use any cryptographic operations during
           an Echo session. In practical terms, this means that the Echo side
           channel session data will be transmitted in the clear, and no
           authentication will be performed by the server or client
           during the session establishment phase. When <option>--no-crypto</option>
           is used, the passphrase supplied with <option>--echo-server</option>
           or <option>--echo-client</option> is ignored.
        </para>

        <para>
           This option must be specified if Nping was compiled without
           openSSL support. Note that, for technical reasons, a passphrase still
           needs to be supplied after the --echo-client or --echo-server flags,
           even though it will be ignored.
        </para>
        
        <para>
           The --no-crypto flag might be useful when setting up a public Echo
           server, because it allows users to connect to the Echo server without
           the need for any passphrase or shared secret. However, it is strongly
           recommended to not use --no-crypto unless absolutely necessary. Public
           Echo servers should be configured to use the passphrase "public" or
           the empty passphrase (--echo-server "") as the use of cryptography
           does not only provide confidentiality and authentication but also
           message integrity.
        </para>

        </listitem>
      </varlistentry>

      <varlistentry>
        <term>          
          <option>--once</option> (Serve one client and quit)
          <indexterm significance="preferred"><primary><option>--once</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
        <para>
           This option asks the Echo server to quit after serving one client.
           This is useful when only a single Echo session wants to be established
           as it eliminates the need to access the remote host to shutdown the
           server.         
        </para>

        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <option>--safe-payloads</option> (Zero application data before echoing a packet)
          <indexterm significance="preferred"><primary><option>--safe-payloads</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
        <para>
           This option asks the Echo server to erase any application layer data
           found in client packets before echoing them. When the option is enabled,
           the Echo server parses the packets received from Echo clients and tries
           to determine if they contain data beyond the transport layer. If such
           data is found, it is overwritten with zeroes before transmitting the
           packets to the appropriate Echo client.
        </para>

        <para>
            Echo servers can handle multiple simultaneous clients running
            multiple echo sessions in parallel. In order to determine which packet
            needs to be echoed to which client and through which session, the Echo
            server uses an heuristic algorithm. Although we have taken every
            security measure that we could think of to prevent that a client
            receives an echoed packet that it did not generate, there is always
            a risk that our algorithm makes a mistake and delivers a packet to
            the wrong client. The --safe-payloads option is useful for public
            echo servers or critical deployments where that kind of mistake
            cannot be afforded.
        </para>

        </listitem>
      </varlistentry>
    </variablelist>

    <para>
        The following examples illustrate how Nping's Echo mode can be used
        to discover intermediate devices.
    </para>

    <example id="nping-man-ex-echo1"><title>Discovering NAT devices</title>
    <indexterm><primary><option>--echo-client</option> (Nping option)</primary><secondary>example of</secondary></indexterm>
    <screen format="linespecific">
    # <userinput>nping --echo-client "public" echo.nmap.org --udp </userinput>

    Starting Nping ( https://nmap.org/nping )
    SENT (1.0970s) UDP 10.1.20.128:53 &gt; 178.79.165.17:40125 ttl=64 id=32523 iplen=28 
    CAPT (1.1270s) UDP 80.38.10.21:45657 &gt; 178.79.165.17:40125 ttl=54 id=32523 iplen=28 
    RCVD (1.1570s) ICMP 178.79.165.17 &gt; 10.1.20.128 Port unreachable (type=3/code=3) ttl=49 id=16619 iplen=56 
    [...]
    SENT (5.1020s) UDP 10.1.20.128:53 &gt; 178.79.165.17:40125 ttl=64 id=32523 iplen=28 
    CAPT (5.1335s) UDP 80.38.10.21:45657 &gt; 178.79.165.17:40125 ttl=54 id=32523 iplen=28 
    RCVD (5.1600s) ICMP 178.79.165.17 &gt; 10.1.20.128 Port unreachable (type=3/code=3) ttl=49 id=16623 iplen=56 
     
    Max rtt: 60.628ms | Min rtt: 58.378ms | Avg rtt: 59.389ms
    Raw packets sent: 5 (140B) | Rcvd: 5 (280B) | Lost: 0 (0.00%)| Echoed: 5 (140B) 
    Tx time: 4.00459s | Tx bytes/s: 34.96 | Tx pkts/s: 1.25
    Rx time: 5.00629s | Rx bytes/s: 55.93 | Rx pkts/s: 1.00
    Nping done: 1 IP address pinged in 6.18 seconds
    </screen>
    </example>

    <para>
    The output clearly shows the presence of a NAT device in the client's local
    network. Note how the captured packet (CAPT) differs from the SENT packet: the
    source address for the original packets is in the reserved 10.0.0.0/8 range,
    while the address seen by the server is 80.38.10.21, the Internet side address
    of the NAT device. The source port was also modified by the device. The line
    starting with RCVD corresponds to the responses generated by the TCP/IP stack
    of the machine where the Echo server is run.
    </para>

    <example id="nping-man-ex-echo2"><title>Discovering a transparent proxy</title>
    <screen format="linespecific">
    # <userinput>nping --echo-client "public" echo.nmap.org --tcp -p80</userinput>

    Starting Nping ( https://nmap.org/nping )
    SENT (1.2160s) TCP 10.0.1.77:41659 &gt; 178.79.165.17:80 S ttl=64 id=3317 iplen=40  seq=567704200 win=1480 
    RCVD (1.2180s) TCP 178.79.165.17:80 &gt; 10.0.1.77:41659 SA ttl=128 id=13177 iplen=44  seq=3647106954 win=16384 &lt;mss 1460&gt;
    SENT (2.2150s) TCP 10.0.1.77:41659 &gt; 178.79.165.17:80 S ttl=64 id=3317 iplen=40  seq=567704200 win=1480 
    SENT (3.2180s) TCP 10.0.1.77:41659 &gt; 178.79.165.17:80 S ttl=64 id=3317 iplen=40  seq=567704200 win=1480 
    SENT (4.2190s) TCP 10.0.1.77:41659 &gt; 178.79.165.17:80 S ttl=64 id=3317 iplen=40  seq=567704200 win=1480 
    SENT (5.2200s) TCP 10.0.1.77:41659 &gt; 178.79.165.17:80 S ttl=64 id=3317 iplen=40  seq=567704200 win=1480 
     
    Max rtt: 2.062ms | Min rtt: 2.062ms | Avg rtt: 2.062ms
    Raw packets sent: 5 (200B) | Rcvd: 1 (46B) | Lost: 4 (80.00%)| Echoed: 0 (0B) 
    Tx time: 4.00504s | Tx bytes/s: 49.94 | Tx pkts/s: 1.25
    Rx time: 5.00618s | Rx bytes/s: 9.19 | Rx pkts/s: 0.20
    Nping done: 1 IP address pinged in 6.39 seconds
    </screen>
    </example>
    
    <para>
    In this example, the output is a bit more tricky. The absence of error 
    messages shows that the Echo client has successfully established an Echo
    session with the server. However, no CAPT packets can be seen in the output.
    This means that none of the transmitted packets reached the server.
    Interestingly, a TCP SYN-ACK packet was received in response to the first
    TCP-SYN packet (and also, it is known that the target host does not have
    port 80 open). This behavior reveals the presence of a transparent web proxy
    cache server (which in this case is an old MS ISA server).
    </para>

</refsect1>


<!-- TIMING AND PERFORMANCE OPTIONS **************************************** -->
 <refsect1 id="nping-man-timing-performance-options">
  <title>Timing and Performance Options</title>

  <variablelist>

      <varlistentry>
        <term>
           <option>--delay <replaceable>time</replaceable></option> (Delay between probes)
          <indexterm significance="preferred"><primary><option>--delay</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option lets you control for how long will Nping wait before
           sending the next probe. Like in many other ping tools, the default
           delay is one second.
           <replaceable>time</replaceable> must be a positive
           integer or floating point number. By default it is specified in
           seconds, however you can give an explicit unit by appending
           <literal>ms</literal> for milliseconds, <literal>s</literal> for seconds,
           <literal>m</literal> for minutes, or <literal>h</literal> for hours
           (e.g. <literal>2.5s</literal>, <literal>45m</literal>, <literal>2h</literal>). 
        </para>
        </listitem>
      </varlistentry>

     
      <varlistentry>
        <term>
          <option>--rate <replaceable>rate</replaceable></option> (Send probes at a given rate)
          <indexterm significance="preferred"><primary><option>--rate</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
            This option specifies the number of probes that Nping should send
            per second. This option and <option>--delay</option> are inverses;
            <option>--rate 20</option> is the same as
            <option>--delay 0.05</option>. If both options are used, only the
            last one in the parameter list counts.
        </para>
        </listitem>
      </varlistentry>
    

    </variablelist>
  </refsect1>









<!-- MISCELLANEOUS OPTIONS ************************************************ -->
 <refsect1 id="nping-man-miscellaneous-options">
  <title>Miscellaneous Options</title>

  <variablelist>

      <varlistentry>
        <term><option>-h</option>,
        <option>--help</option> (Display help)
          <indexterm significance="preferred"><primary><option>--help</option> (Nping option)</primary></indexterm>
          <indexterm significance="preferred"><primary><option>--h</option> (Nping option)</primary><see><option>--help</option></see></indexterm>
        </term>
        <listitem>
          <para>
           Displays help information and exits.
        </para>
        </listitem>
      </varlistentry>

     
      <varlistentry>
        <term>
          <option>-V</option>,
          <option>--version</option> (Display version)
          <indexterm significance="preferred"><primary><option>--version</option> (Nping option)</primary></indexterm>
          <indexterm significance="preferred"><primary><option>-V</option> (Nping option)</primary><see><option>--version</option></see></indexterm>
        </term>
        <listitem>
          <para>
           Displays the program's version number and quits.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <option>-c <replaceable>rounds</replaceable></option>,
          <option>--count <replaceable>rounds</replaceable></option>  (Stop after a given number of rounds)
          <indexterm significance="preferred"><primary><option>--count</option> (Nping option)</primary></indexterm>
          <indexterm significance="preferred"><primary><option>-c</option> (Nping option)</primary><see><option>--count</option></see></indexterm>
        </term>
        <listitem>
          <para>
           This option lets you specify the number of times that Nping should
           loop over target hosts (and in some cases target ports). Nping calls
           these <quote>rounds</quote>. In a basic execution with only one target (and only
           one target port in TCP/UDP modes), the number of rounds matches the
           number of probes sent to the target host. However, in more complex
           executions where Nping is run against multiple targets and multiple
           ports, the number of rounds is the number of times that Nping sends
           a complete set of probes that covers all target IPs and all
           target ports. For example, if Nping is asked to send TCP SYN packets
           to hosts 192.168.1.0-255 and ports 80 and 433, then 256&thinsp;&times;&thinsp;2&nbsp;=&nbsp;512 packets
           are sent in one round. So if you specify <option>-c 100</option>, Nping will
           loop over the different target hosts and ports 100 times, sending
           a total of 256&thinsp;&times;&thinsp;2&thinsp;&times;&thinsp;100&nbsp;=&nbsp;51200 packets. By default Nping runs for
           5 rounds. If a value of 0 is specified, Nping will run continuously.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <option>-e <replaceable>name</replaceable></option>,
          <option>--interface <replaceable>name</replaceable></option>  (Set the network interface to be used)
          <indexterm significance="preferred"><primary><option>--interface</option> (Nping option)</primary></indexterm>
          <indexterm significance="preferred"><primary><option>-e</option> (Nping option)</primary><see><option>--interface</option></see></indexterm>
        </term>
        <listitem>
          <para>
           This option tells Nping what interface should be used to send and
           receive packets. Nping should be able to detect this automatically,
           but it will tell you if it cannot. <replaceable>name</replaceable>
           must be the name of an existing network interface with an assigned
           IP address.

        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term>
           <option>--privileged</option> (Assume that the user is fully privileged)
          <indexterm significance="preferred"><primary><option>--privileged</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           Tells Nping to simply assume that it is privileged enough to perform
           raw socket sends, packet sniffing, and similar operations that
           usually require special privileges. By default Nping quits if such
           operations are requested by a user that has no root or administrator
           privileges. This option may be useful on Linux, BSD or similar
           systems that can be configured to allow unprivileged users to perform
           raw-packet transmissions. The
           <envar>NPING_PRIVILEGED</envar><indexterm><primary><envar>NPING_PRIVILEGED</envar> environment variable</primary></indexterm>
           environment variable
           may be set as an alternative to using <option>--privileged</option>.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
           <option>--unprivileged</option> (Assume that the user lacks raw socket privileges)
          <indexterm significance="preferred"><primary><option>--unprivileged</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           This option is the opposite of <option>--privileged</option>. It tells Nping to treat
           the user as lacking network raw socket and sniffing privileges.
           This is useful for testing, debugging, or when the raw network
           functionality of your operating system is somehow broken. The
           <envar>NPING_UNPRIVILEGED</envar><indexterm><primary><envar>NPING_UNPRIVILEGED</envar> environment variable</primary></indexterm>
           environment variable may be set as an
           alternative to using <option>--unprivileged</option>.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term>
           <option>--send-eth</option> (Use raw ethernet sending)
          <indexterm significance="preferred"><primary><option>--send-eth</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           Asks Nping to send packets at the raw ethernet (data link) layer
           rather than the higher IP (network) layer. By default, Nping chooses
           the one which is generally best for the platform it is running on.
           Raw sockets (IP layer) are generally most efficient for Unix
           machines, while ethernet frames are required for Windows operation
           since Microsoft disabled raw socket support. Nping still uses raw IP
           packets despite this option when there is no other choice (such as
           non-ethernet connections).
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
           <option>--send-ip</option> (Send at raw IP level)
          <indexterm significance="preferred"><primary><option>--send-ip</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
          <para>
           Asks Nping to send packets via raw IP sockets rather than sending
           lower level ethernet frames. It is the complement to the
           <option>--send-eth</option> option.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term>
           <option>--bpf-filter <replaceable>filter spec</replaceable></option>
           <option>--filter <replaceable>filter spec</replaceable></option> (Set custom BPF filter)
          <indexterm significance="preferred"><primary><option>--bpf-filter</option> (Nping option)</primary></indexterm>
          <indexterm significance="preferred"><primary><option>--filter</option> (Nping option)</primary><see>--bpf-filter</see></indexterm>
        </term>
        <listitem>
          <para>
           This option lets you use a custom BPF filter. By default Nping
           chooses a filter that is intended to capture most common responses
           to the particular probes that are sent. For example, when sending
           TCP packets, the filter is set to capture packets whose destination
           port matches the probe's source port or ICMP error messages that may
           be generated by the target or any intermediate device as a result of
           the probe. If for some reason you expect strange packets in response
           to sent probes or you just want to sniff a particular kind of
           traffic, you can specify a custom filter using the BPF syntax used
           by tools like
           tcpdump.<indexterm><primary>tcpdump</primary></indexterm>
           See the documentation at <ulink url="http://www.tcpdump.org/"/> for
           more information.            
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term>
           <option>-H</option>,
           <option>--hide-sent</option> (Do not display sent packets)
          <indexterm significance="preferred"><primary><option>--hide-sent</option> (Nping option)</primary></indexterm>
          <indexterm significance="preferred"><primary><option>-H</option> (Nping option)</primary><see>--hide-sent</see></indexterm>
        </term>
        <listitem>
          <para>
           This option tells Nping not to print information about sent packets.
           This can be useful when using very short inter-probe delays (i.e.,
           when flooding), because printing information to the standard
           output has a computational cost and disabling it can probably
           speed things up a bit. Also, it may be useful when using Nping to
           detect active hosts or open ports (e.g. sending probes to all TCP
           ports in a /24 subnet). In that case, users may not want to see
           thousands of sent probes but just the replies generated by active
           hosts.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
           <option>-N</option>,
           <option>--no-capture</option> (Do not attempt to capture replies)
          <indexterm significance="preferred"><primary><option>--no-capture</option> (Nping option)</primary></indexterm>
          <indexterm significance="preferred"><primary><option>-N</option> (Nping option)</primary><see><option>--no-capture</option></see></indexterm>
        </term>
        <listitem>
          <para>
           This option tells Nping to skip packet capture. This means that
           packets in response to sent probes will not be processed or
           displayed. This can be useful when doing flooding and network stack
           stress tests. Note that when this option is specified, most of
           the statistics shown at the end of the execution will be useless.
           This option does not work with TCP Connect mode.
        </para>
        </listitem>
      </varlistentry>  

    </variablelist>
  </refsect1>


  



<!-- OUTPUT OPTIONS **************************************** -->
 <refsect1 id="nping-man-output-options">
  <title>Output Options</title>

  <variablelist>

      <varlistentry>
        <term>
          <option>-v<optional><replaceable>level</replaceable></optional></option>,
          <option>--verbose <optional><replaceable>level</replaceable></optional></option> (Increase or set verbosity level)
          <indexterm significance="preferred"><primary><option>--verbose</option> (Nping option)</primary></indexterm>
          <indexterm significance="preferred"><primary><option>-v</option> (Nping option)</primary><see><option>--verbose</option></see></indexterm>
        </term>
        <listitem>
          <para>
           Increases the verbosity level, causing Nping to print more
           information during its execution. There are 9 levels of verbosity 
           (-4 to 4). Every instance of <option>-v</option> increments the verbosity level by one 
           (from its default value, level 0). Every instance of option <option>-q</option>
           decrements the verbosity level by one. Alternatively you can specify
           the level directly, as in <option>-v3</option> or
           <option>-v-1</option>. These are the available levels:
           </para>

           <indexterm><primary>verbosity levels of Nping</primary></indexterm>
           <variablelist>
            <varlistentry>
              <term>Level -4</term>
              <listitem>
           <para>
           No output at all. In some circumstances you may not want
           Nping to produce any output (like when one of your work mates is
           watching over your shoulder). In that case level -4 can be useful
           because although you won't see any response packets, probes will
           still be sent.
           </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>Level -3</term>
              <listitem>
           <para>
           Like level -4 but displays fatal error messages so you can
           actually see if Nping is running or it failed due to some error.
           </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>Level -2</term>
              <listitem>
           <para>
           Like level -3 but also displays warnings and recoverable errors.
           </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>Level -1</term>
              <listitem>
           <para>
           Displays traditional run-time information (version, start time,
           statistics, etc.) but does not display sent or received packets.
           </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>Level 0</term>
              <listitem>
           <para>
           This is the default verbosity level. It behaves like level -1 but
           also displays sent and received packets and some other important information.
           </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>Level 1</term>
              <listitem>
           <para>
           Like level 0 but it displays detailed information about
           timing, flags, protocol details, etc.
           </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>Level 2</term>
              <listitem>
           <para>
            Like level 1 but displays very detailed information
            about sent and received packets and other interesting information.
           </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>Level 3</term>
              <listitem>
           <para>
            Like level 2 but also displays the raw hexadecimal dump of sent
            and received packets.
           </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>Level 4 and higher</term>
              <listitem>
           <para>
                Same as level 3.
           </para>
              </listitem>
            </varlistentry>
          </variablelist>

        </listitem>
      </varlistentry>


      <varlistentry>
        <term>
          <option>-q<optional><replaceable>level</replaceable></optional></option>,
          <option>--reduce-verbosity <optional><replaceable>level</replaceable></optional></option> (Decrease verbosity level)
          <indexterm significance="preferred"><primary><option>--reduce-verbosity</option> (Nping option)</primary></indexterm>
          <indexterm significance="preferred"><primary><option>-q</option> (Nping option)</primary><see>--reduce-verbosity</see></indexterm>
        </term>
        <listitem>
          <para>
           Decreases the verbosity level, causing Nping to print less
           information during its execution.
           </para>
           
         </listitem>
      </varlistentry>


     
      <varlistentry>
        <term>
          <option>-d<optional><replaceable>level</replaceable></optional></option> (Increase or set debugging level)
          <indexterm significance="preferred"><primary><option>-d</option> (Nping option)</primary></indexterm>
        </term>
        <listitem>
        
          <para>
           When even verbose mode doesn't provide sufficient data for you,
           debugging is available to flood you with much more! As with the
           <option>-v</option>, debugging is enabled with a command-line
           flag <option>-d</option> and the debug level can be increased by
           specifying it multiple times. There are 7 debugging levels (0 to 6).
           Every instance of <option>-d</option> increments debugging level by
           one. Provide an argument to <option>-d</option> to set the level
           directly; for example <option>-d4</option>.
           </para>

          <para>           
           Debugging output is useful when you suspect a bug in Nping, or if
           you are simply confused as to what Nping is doing and why. As this
           feature is mostly intended for developers, debug lines aren't
           always self-explanatory. You may get something like
<indexterm><primary>Nsock</primary><secondary>debug output of</secondary></indexterm>
<screen>
NSOCK (1.0000s) Callback: TIMER SUCCESS for EID 12; tcpconnect_event_handler<continuation/>(): Received callback of type TIMER with status SUCCESS
</screen>
           If you don't understand a line, your only
           recourses are to ignore it, look it up in the source code, or
           request help from the development list (<citetitle>nmap-dev</citetitle>). Some lines are
           self-explanatory, but the messages become more obscure as the debug
           level is increased. These are the available levels:
           </para>            

           <indexterm><primary>debug levels of Nping</primary></indexterm>
           <variablelist>
            <varlistentry>
              <term>Level 0</term>
              <listitem>
           <para>
           Level 0. No debug information at all. This is the default level. 
           </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>Level 1</term>
              <listitem>
           <para>
           In this level, only very important or high-level debug information
           will be printed.
           </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>Level 2</term>
              <listitem>
           <para>
           Like level 1 but also displays important or medium-level debug
           information
           </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>Level 3</term>
              <listitem>
           <para>
           Like level 2 but also displays regular and low-level debug information.
           </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>Level 4</term>
              <listitem>
           <para>
           Like level 3 but also displays messages only a real Nping freak would
           want to see.
           </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>Level 5</term>
              <listitem>
           <para>
           Like level 4 but it enables basic debug information related to
           external libraries like Nsock.<indexterm><primary>Nsock</primary></indexterm>
           </para>
              </listitem>
            </varlistentry>
            <varlistentry>
              <term>Level 6</term>
              <listitem>
           <para>
           Like level 5 but it enables full, very detailed, debug information
           related to external libraries like Nsock.
           </para>
              </listitem>
            </varlistentry>
          </variablelist>

        </listitem>
      </varlistentry>

    </variablelist>
  </refsect1>
   
  <refsect1 id="nping-man-bugs">
    <title>Bugs</title>
    <indexterm><primary>bugs, reporting</primary></indexterm>

    <para>Like its authors, Nping isn't perfect.  But you can help make
    it better by sending bug reports or even writing patches.  If Nping
    doesn't behave the way you expect, first upgrade to the latest
    version available from <ulink
    url="https://nmap.org"/>.  If the problem persists,
    do some research to determine whether it has already been
    discovered and addressed.  Try searching for the problem or error message on
    Google since that aggregates so many forums.  If nothing comes of this, create an Issue on our tracker
    (<ulink url="http://issues.nmap.org"/>) and/or mail a bug report to
    <email>dev@nmap.org</email>.  If you subscribe to the nmap-dev
    list before posting, your message will bypass moderation and get
    through more quickly.  Subscribe at <ulink
    url="https://nmap.org/mailman/listinfo/dev"/>. Please include everything
    you have learned about the problem, as well as what version of
    Nping you are using and what operating system version it is
    running on.  Other suggestions for improving Nping may be sent to
    the Nmap dev mailing list as well.</para>

    <para>If you are able to write a patch improving Nping or fixing a
    bug, that is even better!  Instructions for submitting patches or
    git pull requests are available from <ulink
    url="https://github.com/nmap/nmap/blob/master/CONTRIBUTING.md"/></para>

    <para>Particularly sensitive issues such as a security reports may
    be sent directly to Fyodor directly at
    <email>fyodor@nmap.org</email>.  All other reports and comments
    should use the dev list or issue tracker instead because more
    people read, follow, and respond to those.</para>
    
  </refsect1>

  <refsect1 id="nping-man-author">
    <title>Authors</title>

    <para>Luis MartinGarcia <email>luis.mgarc@gmail.com</email> (<ulink url="http://www.luismg.com" />)</para>

    <para>Fyodor <email>fyodor@nmap.org</email> (<ulink url="https://insecure.org" />)</para>

  </refsect1>


</refentry>