ping

PING(8)                System Manager's Manual: iputils                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  node-
       info_option] [-w deadline] [-W timeout] [-p pattern] [-Q tos] [-s pack-
       etsize] [-S sndbuf] [-t ttl] [-T timestamp option] [hop  ...]  destina-
       tion

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
       (``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.

       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).  Intermedi-
       ate 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  inter-
              val  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 time-
              out 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 hun-
              dred 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.  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 val-
              ues less than 0.2 seconds.

       -I interface
              interface is either an address, or an interface name.  If inter-
              face  is  an address, it sets source address to specified inter-
              face address.  If interface in an interface name, it sets source
              interface  to specified interface.  For IPv6, when doing ping to
              a link-local scope address, link specification (by the '%'-nota-
              tion in destination, or by this option) is required.

       -l preload
              If  preload is specified, ping sends that many packets not wait-
              ing 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  vari-
              ety 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  spe-
                     cific 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 sepa-
              rate data, and bits 2-7 (highest 6 bits) of Differentiated  Ser-
              vices  Codepoint  (DSCP).   In RFC2481 and RFC3168, bits 0-1 are
              used for ECN.

              Historically (RFC1349, obsoleted by RFC2474), these were  inter-
              preted  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 run-
       ning. 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  dis-
       played.  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 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
       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  indi-
       cate  broken  hardware somewhere in the ping packet's path (in the net-
       work or in the hosts).

TRYING DIFFERENT DATA PATTERNS
       The (inter)network layer should never treat packets differently depend-
       ing  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 pat-
       tern 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 trans-
       mit 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 man-
       age 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 decre-
       ment 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  tel-
       net(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  condi-
         tions.

SEE ALSO
       netstat(1), ifconfig(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 funcionality as before.

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 cre-
       ate an ICMP echo socket.  The program may be used as set-uid root.

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

iputils-161105                   28 June 2019                          PING(8)
Man Pages Copyright Respective Owners. Site Copyright (C) 1994 - 2021 Hurricane Electric. All Rights Reserved.