NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ICMP PACKET DETAILS | DUPLICATE AND DAMAGED PACKETS | TRYING DIFFERENT DATA PATTERNS | TTL DETAILS | BUGS | SEE ALSO | HISTORY | SECURITY | AVAILABILITY | COLOPHON

PING(8)               System Manager's Manual: iputils               PING(8)

NAME         top

       ping, ping6 - send ICMP ECHO_REQUEST to network hosts

SYNOPSIS         top

       ping [-aAbBdDfhLnOqrRUvV] [-c count] [-F flowlabel] [-i interval] [-I
       interface] [-l preload] [-m mark] [-M pmtudisc_option] [-N
       nodeinfo_option] [-w deadline] [-W timeout] [-p pattern] [-Q tos] [-s
       packetsize] [-S sndbuf] [-t ttl] [-T timestamp option] [hop ...]
       destination

DESCRIPTION         top

       ping uses the ICMP protocol's mandatory ECHO_REQUEST datagram to
       elicit an ICMP ECHO_RESPONSE from a host or gateway.  ECHO_REQUEST
       datagrams (``pings'') have an IP and ICMP header, followed by a
       struct timeval and then an arbitrary number of ``pad'' bytes used to
       fill out the packet.

       ping6 is IPv6 version of ping, and can also send Node Information
       Queries (RFC4620).  Intermediate hops may not be allowed, because
       IPv6 source routing was deprecated (RFC5095).

OPTIONS         top

       -a     Audible ping.

       -A     Adaptive ping. Interpacket interval adapts to round-trip time,
              so that effectively not more than one (or more, if preload is
              set) unanswered probe is present in the network. Minimal
              interval is 200msec for not super-user.  On networks with low
              rtt this mode is essentially equivalent to flood mode.

       -b     Allow pinging a broadcast address.

       -B     Do not allow ping to change source address of probes.  The
              address is bound to one selected when ping starts.

       -c count
              Stop after sending count ECHO_REQUEST packets. With deadline
              option, ping waits for count ECHO_REPLY packets, until the
              timeout expires.

       -d     Set the SO_DEBUG option on the socket being used.
              Essentially, this socket option is not used by Linux kernel.

       -D     Print timestamp (unix time + microseconds as in gettimeofday)
              before each line.

       -f     Flood ping. For every ECHO_REQUEST sent a period ``.'' is
              printed, while for ever ECHO_REPLY received a backspace is
              printed.  This provides a rapid display of how many packets
              are being dropped.  If interval is not given, it sets interval
              to zero and outputs packets as fast as they come back or one
              hundred times per second, whichever is more.  Only the super-
              user may use this option with zero interval.

       -F flow label
              ping6 only.  Allocate and set 20 bit flow label (in hex) on
              echo request packets.  If value is zero, kernel allocates
              random flow label.

       -h     Show help.

       -i interval
              Wait interval seconds between sending each packet.  The
              default is to wait for one second between each packet
              normally, or not to wait in flood mode. Only super-user may
              set interval to values less 0.2 seconds.

       -I interface
              interface is either an address, or an interface name.  If
              interface is an address, it sets source address to specified
              interface address.  If interface in an interface name, it sets
              source interface to specified interface.  For ping6, when
              doing ping to a link-local scope address, link specification
              (by the '%'-notation in destination, or by this option) is
              required.

       -l preload
              If preload is specified, ping sends that many packets not
              waiting for reply.  Only the super-user may select preload
              more than 3.

       -L     Suppress loopback of multicast packets.  This flag only
              applies if the ping destination is a multicast address.

       -m mark
              use mark to tag the packets going out. This is useful for
              variety of reasons within the kernel such as using policy
              routing to select specific outbound processing.

       -M pmtudisc_opt
              Select Path MTU Discovery strategy.  pmtudisc_option may be
              either do (prohibit fragmentation, even local one), want (do
              PMTU discovery, fragment locally when packet size is large),
              or dont (do not set DF flag).

       -N nodeinfo_option
              ping6 only.  Send ICMPv6 Node Information Queries (RFC4620),
              instead of Echo Request.  CAP_NET_RAW capability is required.

              help   Show help for NI support.

              name   Queries for Node Names.

              ipv6   Queries for IPv6 Addresses. There are several IPv6
                     specific flags.

                     ipv6-global
                            Request IPv6 global-scope addresses.

                     ipv6-sitelocal
                            Request IPv6 site-local addresses.

                     ipv6-linklocal
                            Request IPv6 link-local addresses.

                     ipv6-all
                            Request IPv6 addresses on other interfaces.

              ipv4   Queries for IPv4 Addresses.  There is one IPv4 specific
                     flag.

                     ipv4-all
                            Request IPv4 addresses on other interfaces.

              subject-ipv6=ipv6addr
                     IPv6 subject address.

              subject-ipv4=ipv4addr
                     IPv4 subject address.

              subject-name=nodename
                     Subject name.  If it contains more than one dot, fully-
                     qualified domain name is assumed.

              subject-fqdn=nodename
                     Subject name.  Fully-qualified domain name is always
                     assumed.

       -n     Numeric output only.  No attempt will be made to lookup
              symbolic names for host addresses.

       -O     Report outstanding ICMP ECHO reply before sending next packet.
              This is useful together with the timestamp -D to log output to
              a diagnostic file and search for missing answers.

       -p pattern
              You may specify up to 16 ``pad'' bytes to fill out the packet
              you send.  This is useful for diagnosing data-dependent
              problems in a network.  For example, -p ff will cause the sent
              packet to be filled with all ones.

       -q     Quiet output.  Nothing is displayed except the summary lines
              at startup time and when finished.

       -Q tos Set Quality of Service -related bits in ICMP datagrams.  tos
              can be decimal (ping only) or hex number.

              In RFC2474, these fields are interpreted as 8-bit
              Differentiated Services (DS), consisting of: bits 0-1 (2
              lowest bits) of separate data, and bits 2-7 (highest 6 bits)
              of Differentiated Services Codepoint (DSCP).  In RFC2481 and
              RFC3168, bits 0-1 are used for ECN.

              Historically (RFC1349, obsoleted by RFC2474), these were
              interpreted as: bit 0 (lowest bit) for reserved (currently
              being redefined as congestion control), 1-4 for Type of
              Service and bits 5-7 (highest bits) for Precedence.

       -r     Bypass the normal routing tables and send directly to a host
              on an attached interface.  If the host is not on a directly-
              attached network, an error is returned.  This option can be
              used to ping a local host through an interface that has no
              route through it provided the option -I is also used.

       -R     ping only.  Record route.  Includes the RECORD_ROUTE option in
              the ECHO_REQUEST packet and displays the route buffer on
              returned packets.  Note that the IP header is only large
              enough for nine such routes.  Many hosts ignore or discard
              this option.

       -s packetsize
              Specifies the number of data bytes to be sent.  The default is
              56, which translates into 64 ICMP data bytes when combined
              with the 8 bytes of ICMP header data.

       -S sndbuf
              Set socket sndbuf. If not specified, it is selected to buffer
              not more than one packet.

       -t ttl ping only.  Set the IP Time to Live.

       -T timestamp option
              Set special IP timestamp options.  timestamp option may be
              either tsonly (only timestamps), tsandaddr (timestamps and
              addresses) or tsprespec host1 [host2 [host3 [host4]]]
              (timestamp prespecified hops).

       -U     Print full user-to-user latency (the old behaviour). Normally
              ping prints network round trip time, which can be different
              f.e. due to DNS failures.

       -v     Verbose output.

       -V     Show version and exit.

       -w deadline
              Specify a timeout, in seconds, before ping exits regardless of
              how many packets have been sent or received. In this case ping
              does not stop after count packet are sent, it waits either for
              deadline expire or until count probes are answered or for some
              error notification from network.

       -W timeout
              Time to wait for a response, in seconds. The option affects
              only timeout in absence of any responses, otherwise ping waits
              for two RTTs.

       When using ping for fault isolation, it should first be run on the
       local host, to verify that the local network interface is up and
       running. Then, hosts and gateways further and further away should be
       ``pinged''. Round-trip times and packet loss statistics are computed.
       If duplicate packets are received, they are not included in the
       packet loss calculation, although the round trip time of these
       packets is used in calculating the minimum/average/maximum round-trip
       time numbers.  When the specified number of packets have been sent
       (and received) or if the program is terminated with a SIGINT, a brief
       summary is displayed. Shorter current statistics can be obtained
       without termination of process with signal SIGQUIT.

       If ping does not receive any reply packets at all it will exit with
       code 1. If a packet count and deadline are both specified, and fewer
       than count packets are received by the time the deadline has arrived,
       it will also exit with code 1.  On other error it exits with code 2.
       Otherwise it exits with code 0. This makes it possible to use the
       exit code to see if a host is alive or not.

       This program is intended for use in network testing, measurement and
       management.  Because of the load it can impose on the network, it is
       unwise to use ping during normal operations or from automated
       scripts.

ICMP PACKET DETAILS         top

       An IP header without options is 20 bytes.  An ICMP ECHO_REQUEST
       packet contains an additional 8 bytes worth of ICMP header followed
       by an arbitrary amount of data.  When a packetsize is given, this
       indicated the size of this extra piece of data (the default is 56).
       Thus the amount of data received inside of an IP packet of type ICMP
       ECHO_REPLY will always be 8 bytes more than the requested data space
       (the ICMP header).

       If the data space is at least of size of struct timeval ping uses the
       beginning bytes of this space to include a timestamp which it uses in
       the computation of round trip times.  If the data space is shorter,
       no round trip times are given.

DUPLICATE AND DAMAGED PACKETS         top

       ping will report duplicate and damaged packets.  Duplicate packets
       should never occur, and seem to be caused by inappropriate link-level
       retransmissions.  Duplicates may occur in many situations and are
       rarely (if ever) a good sign, although the presence of low levels of
       duplicates may not always be cause for alarm.

       Damaged packets are obviously serious cause for alarm and often
       indicate broken hardware somewhere in the ping packet's path (in the
       network or in the hosts).

TRYING DIFFERENT DATA PATTERNS         top

       The (inter)network layer should never treat packets differently
       depending on the data contained in the data portion.  Unfortunately,
       data-dependent problems have been known to sneak into networks and
       remain undetected for long periods of time.  In many cases the
       particular pattern that will have problems is something that doesn't
       have sufficient ``transitions'', such as all ones or all zeros, or a
       pattern right at the edge, such as almost all zeros.  It isn't
       necessarily enough to specify a data pattern of all zeros (for
       example) on the command line because the pattern that is of interest
       is at the data link level, and the relationship between what you type
       and what the controllers transmit can be complicated.

       This means that if you have a data-dependent problem you will
       probably have to do a lot of testing to find it.  If you are lucky,
       you may manage to find a file that either can't be sent across your
       network or that takes much longer to transfer than other similar
       length files.  You can then examine this file for repeated patterns
       that you can test using the -p option of ping.

TTL DETAILS         top

       The TTL value of an IP packet represents the maximum number of IP
       routers that the packet can go through before being thrown away.  In
       current practice you can expect each router in the Internet to
       decrement the TTL field by exactly one.

       The TCP/IP specification states that the TTL field for TCP packets
       should be set to 60, but many systems use smaller values (4.3 BSD
       uses 30, 4.2 used 15).

       The maximum possible value of this field is 255, and most Unix
       systems set the TTL field of ICMP ECHO_REQUEST packets to 255.  This
       is why you will find you can ``ping'' some hosts, but not reach them
       with telnet(1) or ftp(1).

       In normal operation ping prints the TTL value from the packet it
       receives.  When a remote system receives a ping packet, it can do one
       of three things with the TTL field in its response:

       · Not change it; this is what Berkeley Unix systems did before the
         4.3BSD Tahoe release. In this case the TTL value in the received
         packet will be 255 minus the number of routers in the round-trip
         path.

       · Set it to 255; this is what current Berkeley Unix systems do.  In
         this case the TTL value in the received packet will be 255 minus
         the number of routers in the path from the remote system to the
         pinging host.

       · Set it to some other value. Some machines use the same value for
         ICMP packets that they use for TCP packets, for example either 30
         or 60.  Others may use completely wild values.

BUGS         top

       · Many Hosts and Gateways ignore the RECORD_ROUTE option.

       · The maximum IP header length is too small for options like
         RECORD_ROUTE to be completely useful.  There's not much that can be
         done about this, however.

       · Flood pinging is not recommended in general, and flood pinging the
         broadcast address should only be done under very controlled
         conditions.

SEE ALSO         top

       netstat(1), ifconfig(8).

HISTORY         top

       The ping command appeared in 4.3BSD.

       The version described here is its descendant specific to Linux.

SECURITY         top

       ping requires CAP_NET_RAW capability to be executed 1) if the program
       is used for non-echo queries (See -N option), or 2) if kernel does
       not support non-raw ICMP sockets, or 3) if the user is not allowed to
       create an ICMP echo socket.  The program may be used as set-uid root.

AVAILABILITY         top

       ping is part of iputils package and the latest versions are
       available in source form at
       http://www.skbuff.net/iputils/iputils-current.tar.bz2.

COLOPHON         top

       This page is part of the iputils (IP utilities) project.  Information
       about the project can be found at ⟨http://www.skbuff.net/iputils/⟩.
       If you have a bug report for this manual page, send it to
       yoshfuji@skbuff.net, netdev@vger.kernel.org.  This page was obtained
       from the project's upstream Git repository 
       ⟨git://git.linux-ipv6.org/gitroot/iputils.git⟩ on 2016-10-04.  If you
       discover any rendering problems in this HTML version of the page, or
       you believe there is a better or more up-to-date source for the page,
       or you have corrections or improvements to the information in this
       COLOPHON (which is not part of the original manual page), send a mail
       to man-pages@man7.org

iputils-151218                 04 October 2016                       PING(8)