Quick ?s
Cheat Sheets
Man Pages
The Lynx
PING(8) 	       System Managers Manual: iputils		      PING(8)

       ping, ping6 - send ICMP ECHO_REQUEST to network hosts

       ping  [ -LRUbdfnqrvVaAB]  [ -c count]  [ -i interval]  [ -l preload]  [
       -p pattern]  [ -s packetsize]  [ -t ttl]  [ -w deadline]  [ -F  flowla
       bel]  [ -I interface]  [ -M hint]  [ -Q tos]  [ -S sndbuf]  [ -T times
       tamp option]  [ -W timeout]  [ hop ...]	destination

       ping uses the ICMP protocols 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

       -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.

       -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.

       -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  hun
	      dred  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  val
	      ues 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 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.

       -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.

       -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  rede
	      fined  as  congestion  control), 1-4 for Type of Service and 5-7
	      for Precedence.  Possible settings for Type of Service are: min
	      imal cost: 0x02, reliability: 0x04, throughput: 0x08, low delay:
	      0x10.  Multiple TOS bits should not be set simultaneously.  Pos
	      sible settings for special Precedence range from priority (0x20)
	      to net control (0xe0).  You must be root (CAP_NET_ADMIN capabil
	      ity) 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 Differenti
	      ated Services (DS), consisting of: bits  0-1  of	separate  data
	      (ECN  will  be  used, here), and bits 2-7 of Differentiated Ser
	      vices 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 (pro
	      hibit  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  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.

       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 packets path (in the
       network 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-
       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 doesnt have  sufficient
       transitions,  such  as all ones or all zeros, or a pattern right at
       the edge, such as almost all zeros.  It	isnt  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 cant 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
       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.	Theres 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_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   for   anonymous  ftp  ftp://ftp.inr.ac.ru/ip-rout

iputils-020927			30 January 2007 		       PING(8)

Yals.net is © 1999-2009 Crescendo Communications
Sharing tech info on the web for more than a decade!
This page was generated Thu Apr 30 17:05:32 2009