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       ping, ping6 - send ICMP ECHO_REQUEST to network hosts


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


       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 can also send Node Information Queries (RFC4620).


       -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 probes 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.

       -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.

       -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.

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

       -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.

       -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 address
              Set  source address to specified interface address. Argument may
              be numeric IP address or name of device. When pinging IPv6 link-
              local address 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.

       -N nioption
              Send ICMPv6 Node Information Queries (RFC4620), instead of  Echo

              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.

       -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.

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

       -Q tos Set Quality of Service -related bits in ICMP datagrams.  tos can
              be either decimal or hex number.  Traditionally (RFC1349), these
              have been  interpreted  as:  0  for  reserved  (currently  being
              redefined  as  congestion  control), 1-4 for Type of Service and
              5-7 for Precedence.  Possible settings for Type of Service  are:
              minimal  cost:  0x02,  reliability:  0x04, throughput: 0x08, low
              delay:  0x10.    Multiple   TOS   bits   should   not   be   set
              simultaneously.   Possible settings for special Precedence range
              from priority (0x20) to net control (0xe0).  You  must  be  root
              (CAP_NET_ADMIN  capability) to use Critical or higher precedence
              value.  You cannot set bit 0x01 (reserved) unless ECN  has  been
              enabled  in  the  kernel.   In  RFC2474,  these  fields has been
              redefined as 8-bit Differentiated Services (DS), consisting  of:
              bits 0-1 of separate data (ECN will be used, here), and bits 2-7
              of Differentiated Services Codepoint (DSCP).

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

       -R     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.

       -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.

       -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 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).

       -M hint
              Select Path MTU Discovery  strategy.   hint  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).

       -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 absense 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:

       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

       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

       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.


       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 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


       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_RAWIO capability to be executed. It may be used
       as set-uid root.


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