PING(8)                                                   PING(8)

     NAME
          ping - send ICMP ECHO_REQUEST to network hosts

     SYNOPSIS
          ping [-aAbBdDfhLnOqrRUvV46] [-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
          ping uses the ICMP protocol's mandatory ECHO_REQUEST
          datagram to elicit an ICMP ECHO_RESPONSE from a host or
          gateway. ECHO_REQUEST datagrams (lqpingsrq) have an IP and
          ICMP header, followed by a struct timeval and then an
          arbitrary number of lqpadrq bytes used to fill out the packet.

          ping works with both IPv4 and IPv6. Using only one of them
          explicitly can be enforced by specifying -4 or -6.

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

     OPTIONS
          -4
              Use IPv4 only.

          -6
              Use IPv6 only.

          -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 unless 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.

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     PING(8)                                                   PING(8)

          -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 lq.rq is
              printed, while for every 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
              IPv6 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. Real
              number allowed with dot as a decimal separator
              (regardless locale setup). 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 than 0.2 seconds.

          -I interface
              interface is either an address, an interface name or a
              VRF name. If interface is an address, it sets source
              address to specified interface address. If interface is
              an interface name, it sets source interface to specified
              interface. If interface is a VRF name, each packet is
              routed using the corresponding routing table; in this
              case, the -I option can be repeated to specify a source
              address. NOTE: For IPv6, when doing ping to a link-local
              scope address, link specification (by the '%'-notation
              in destination, or by this option) can be used but it is
              no longer required.

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     PING(8)                                                   PING(8)

          -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
              IPv6 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

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     PING(8)                                                   PING(8)

                      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 lqpadrq 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.

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     PING(8)                                                   PING(8)

          -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. Do not suppress DUP replies when pinging
              multicast address.

          -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.

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     PING(8)                                                   PING(8)

          -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. Real number allowed
              with dot as a decimal separator (regardless locale
              setup). 0 means infinite timeout.

          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 lqpingedrq. 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/mdev round-trip time numbers.

          Population standard deviation (mdev), essentially an average
          of how far each ping RTT is from the mean RTT. The higher
          mdev is, the more variable the RTT is (over time). With a
          high RTT variability, you will have speed issues with bulk
          transfers (they will take longer than is strictly speaking
          necessary, as the variability will eventually cause the
          sender to wait for ACKs) and you will have middling to poor
          VoIP quality.

          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
          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 indicates 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

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     PING(8)                                                   PING(8)

          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
          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
          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
          lqtransitionsrq, 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
          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

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     PING(8)                                                   PING(8)

          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 lqpingrq 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:

              +o 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.

              +o 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.

              +o 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
              +o Many Hosts and Gateways ignore the RECORD_ROUTE
              option.

              +o 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.

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

     SEE ALSO
          ip(8), ss(8).

     HISTORY
          The ping command appeared in 4.3BSD.

          The version described here is its descendant specific to
          Linux.

          As of version s20150815, the ping6 binary doesn't exist
          anymore. It has been merged into ping. Creating a symlink
          named ping6 pointing to ping will result in the same
          functionality as before.

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     PING(8)                                                   PING(8)

     SECURITY
          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
          ping is part of iputils package.

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