ping man page on Tru64

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ping(8)								       ping(8)

NAME
       ping - Sends ICMP ECHO_REQUEST packets to network hosts

SYNOPSIS
       /usr/sbin/ping  [-dfnqruvLR] [-b num] [-c count] [-i wait] [-l preload]
       [-p  pattern]  [-s  packetsize]	[-tnumber]   [-I   interface]	[-G[!]
       @addr1@addr2...] [-V version] host

OPTIONS
       Specifies the size of the receive buffer.  You can use this when speci‐
       fying very large packet sizes with the -s option.  By default, the size
       of  the receive buffer is set to 48K or to the size specified by the -s
       option, whichever is greater.  The -b  option  overrides	 the  default.
       Stops  after  sending (and receiving) count ECHO_RESPONSE packets.  Set
       the SO_DEBUG option on the socket being used.   Floods  ping.   Outputs
       packets as fast as they come back or 100 times per second, whichever is
       more. For every ECHO_REQUEST sent, a (dot) is printed, while for	 every
       ECHO_REPLY  received a backspace is used. This provides a rapid display
       of how many packets are being dropped. Only the superuser may use  this
       option.	 This  can  be	very hard on a network and should be used with
       caution (see Cautions).	Specifies the  source  route  for  packets  to
       travel to the destination host.	The route consists of one or more node
       names or addresses.  Use the ampersand character (@) to separate multi‐
       ple addresses.  You can specify up to 10 addresses.

	      The  exclamation mark (!) indicates that this is a strict source
	      route; ping uses only the specified hosts for intermediate hops.

	      If any of the specified addresses is a  hostname,	 a  lookup  is
	      performed	 and the protocol common to all addresses is used.  If
	      there is no common protocol (for example, one host has only IPv4
	      address  and  one	 host  has  only  IPv6	address),  an error is
	      printed.	If all hosts have both IPv4 and IPv6  addresses,  IPv6
	      is  used.	  You  can  override  this  option with the -V option.
	      Waits wait seconds between sending each packet.  The default  is
	      to  wait for 1 second between each packet. This option is incom‐
	      patible with the -f option.  [IPv6 only]	 Sends packets through
	      interface	 instead of using the interface specified in the rout‐
	      ing tables for the host.	Displays every 100th  reply  only  and
	      displays a message indicating lost packets.

	      A packet loss rate of just 1% is enough to seriously impact UDP-
	      based protocols like NFS.	 This option enables  you  to  measure
	      loss  rates and to determine how bursty they are.	 All lost mes‐
	      sages are reported with the following message:

	      Lost sequence number(s) number

	      The number value is a single number or a range or	 numbers.   If
	      preload  is  specified,  ping sends that many packets as fast as
	      possible before falling into its normal mode of  behavior.  Only
	      the  superuser  may use this option.  This can be very hard on a
	      network and should be used with caution (see Cautions).  Numeric
	      output  only.  No attempt will be made to look up symbolic names
	      for host addresses. This occurs only when displaying ICMP	 pack‐
	      ets  other  than	ECHO_RESPONSE.	 You  may specify up to 16 pad
	      bytes to fill out the packet you send.  This is useful for diag‐
	      nosing  data-dependent problems in a network. For example, -p ff
	      will cause the sent packet to be	filled	with  all  1s  (ones).
	      Quiets output.  Nothing is displayed except the summary lines at
	      start-up time  and  when	finished.   [ICMP  over	 IPv4  only]
	      Records	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.  Bypasses
	      the  normal  routing  tables  and directly sends to a host on an
	      attached network.	 If the host is not  on	 a  directly  attached
	      network,	an error is returned.  This option can be used to send
	      ping to a local host  through an interface  that	has  no	 route
	      through  it  (for	 example,  after  the interface was dropped by
	      routed).	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.  Sets the timeout
	      period  (in  seconds)  for ping to wait before terminating.  The
	      default timeout period is 10 seconds.  This option is only  use‐
	      ful  with -c 1 option.  Displays the time in microseconds (three
	      decimal places). In order to ensure this microsecond  precision,
	      the  NTP_TIME  and  MICRO_TIME  kernel  options  must be on.  By
	      default NTP_TIME and MICRO_TIME  kernel  options	are  off.   If
	      these  kernel  options are off and this option is used, the time
	      is displayed to  three  decimal  places,	but  in	 milliseconds.
	      Specifies verbose output.	 ICMP packets other than ECHO_RESPONSE
	      that are received are listed.  Specifies the  Internet  Protocol
	      (IP) version number to enable the resolver to return the correct
	      address.	If you are issuing a ping command to a host name  (not
	      IP  address)  that  has both IPv4 and IPv6 addresses, by default
	      the command is issued using  the	IPv6  address.	 Use  the  -V4
	      option if you want to use the IPv4 address.

DESCRIPTION
       The ping command uses the ICMP (Internet Control Message Protocol) pro‐
       tocol's mandatory ECHO_REQUEST datagram to elicit an ICMP ECHO_RESPONSE
       from  the  specified host or gateway host, where host is a network name
       or IP address.  ECHO_REQUEST datagrams (pings)  have  an	 IP  (Internet
       Protocol)  and  ICMP  header,  followed by a struct timeval and then an
       arbitrary number of pad bytes used to fill out the packet.  The operat‐
       ing system supports both ICMPv4 and ICMPv6.

       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 sent
       the ping command.  Round-trip times and packet loss statistics are com‐
       puted.  If duplicate packets are received, they are not included in the
       packet loss calculations, although the round-trip time of these packets
       is  used	 in  calculating  the minimum, average, and 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 sum‐
       mary is displayed.

       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.

   ICMPv4 Packet Details
       An IPv4 header without options is  20  bytes.  An  ICMPv4  ECHO_REQUEST
       packet  contains	 an additional 8 bytes worth of ICMPv4 header followed
       by an arbitrary amount of data. When a packetsize is given, this	 indi‐
       cates  the  size of this extra piece of data (the default is 56). Thus,
       the amount of data received inside of  an  IPv4	packet	of  type  ICMP
       ECHO_REPLY  will	 always	 be 8 bytes more than the requested data space
       (the ICMPv4 header).

       If the data space is at least 8 bytes large,  ping  uses	 the  first  8
       bytes of this space to include a timestamp, which it uses in the compu‐
       tation of round-trip times. If less than 8 bytes of pad are  specified,
       no round-trip times are given.

   Duplicate and Damaged Packets
       The  ping  command 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 does not have sufficient
       transitions, such as all 1s (ones) or all  0s  (zeros),	or  a  pattern
       right  at the edge, such as almost all 0s (zeros).  It is not necessar‐
       ily enough to specify a data pattern of all 0s (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 enter  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  man‐
       age  to	find  a file that either cannot 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.

   IPv4 TTL Details
       The TTL value of an IPv4 packet represents the maximum number  of  IPv4
       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 1 (one).

       The  TCP/IP  specification  states  that	 the TTL field for TCP packets
       should be set to 60, but many systems use smaller values	 (4.3BSD  uses
       30, 4.2BSD used 15).

       The maximum possible value of this field is 255, and most UNIX compati‐
       ble systems set the TTL field of ICMP ECHO_REQUEST packets to 255. This
       is  why	you  will find you can use the ping command on some hosts, but
       not reach them with telnet or ftp.

       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 compatible systems did before the 4.3BSD release.
       In this case, the TTL value in the received packet will	be  255	 minus
       the  number  of routers in the round-trip path.	Set it to 255; this is
       what current Berkeley UNIX compatible 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  host	that  received
       the  ping  command.   Set it to some other value. Some machines use the
       same value for ICMPv4 packets that they use for TCP packets; for	 exam‐
       ple, either 30 or 60. Others may use completely wild values.

CAUTIONS
       Many hosts and gateways ignore the RECORD_ROUTE option.

       Flooding and preloading the ping command is not recommended in general,
       and flooding ping on the broadcast address should only  be  done	 under
       very controlled conditions.

FILES
       Specifies the command path

SEE ALSO
       Commands: netstat(1), ifconfig(8)

       Daemons: gated(8), routed(8)

       RFC 792, Internet Control Message Protocol, Postel, J.

       RFC  2463,  Internet Control Message Protocol (ICMPv6) for the Internet
       Protocol Version 6 (IPv6) Specification, Conta, A., and Deering, S.

								       ping(8)
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