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ping(8)								       ping(8)

       ping, ping6 - send ICMP ECHO_REQUEST to network hosts

       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}

       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 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 ad‐
	      dress is bound to one selected when ping starts.

       Stop after sending count ECHO_REQUEST
	      packets. With deadline [ping(8)] 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 print‐
	      ed, 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 val‐
	      ues less 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 ping6, 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

       -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  ei‐
	      ther  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), in‐
	      stead of Echo Request.

	      help   Show help for NI support.

	      name   Queries for Node Names.

	      ipv6   Queries for IPv6 Addresses. There are several  IPv6  spe‐
		     cific 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 as‐

       -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 re‐
	      defined 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-at‐
	      tached  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  re‐
	      turned  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 ei‐
	      ther tsonly (only timestamps),  tsandaddr	 (timestamps  and  ad‐
	      dresses)	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.

       Specify a timeout, in seconds, before
	      ping exits regardless of how many packets have been sent or  re‐
	      ceived.  In  this	 case ping does not stop after count [ping(8)]
	      packet are sent, it waits either for deadline  [ping(8)]	expire
	      or  until	 count [ping(8)] 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  lo‐
       cal 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 calcula‐
       tion,  although	the round trip time of these packets is used in calcu‐
       lating 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 [ping(8)] and deadline [ping(8)] are both
       specified, and fewer than count [ping(8)] packets are received  by  the
       time the deadline [ping(8)] 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 ar‐
       bitrary 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.

       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).

       The (inter)network layer should never treat packets differently depend‐
       ing on the data contained in the data portion.  Unfortunately, data-de‐
       pendent problems have been known to sneak into networks and remain  un‐
       detected	 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.

       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 re‐
       ceives.	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 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	condi‐

       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. It may be used as
       set-uid root.

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

iputils-			13 August 2013			       ping(8)

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