ping, ping6 - send ICMP ECHO_REQUEST to network hosts


   ping  [-aAbBdDfhLnOqrRUvV6] [-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  ...]


   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

   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).


   -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

   -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.

                        Request IPv6 global-scope addresses.

                        Request IPv6 site-local addresses.

                        Request IPv6 link-local addresses.

                        Request IPv6 addresses on other interfaces.

          ipv4   Queries for IPv4 Addresses.  There is one  IPv4  specific

                        Request IPv4 addresses on other interfaces.

                 IPv6 subject address.

                 IPv4 subject address.

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

                 Subject name.   Fully-qualified  domain  name  is  always

   -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.


   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

   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.


   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).


   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.


   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

   · 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

   · 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.


   · 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


   netstat(1), ifconfig(8).


   The ping command appeared in 4.3BSD.

   The version described here is its descendant specific to Linux.


   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.


   ping  is part of iputils package and the latest versions are  available
   in    source     form     at


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