NAME

       ping — send ICMP ECHO_REQUEST packets to network hosts

SYNOPSIS

       ping [option ...] host ...

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.

OPTIONS

       --address
               Send ICMP_ADDRESS packets (root only).

       --mask  Same as --address.

       --echo  Send ICMP_ECHO packets (default).

       --timestamp
               Send ICMP_TIMESTAMP packets.

       -t, --type type
               Send type packets.

       -c, --count count
               Stop after sending (and receiving) count ECHO_RESPONSE packets.

       -d, --debug
               Set the SO_DEBUG option on the socket being used.

       -f, --flood
               Flood ping.  Outputs packets as fast as they come back or one hundred times per second, whichever
               is more.  For every ECHO_REQUEST sent a  period  "."  is  printed,  while  for  every  ECHO_REPLY
               received  a  backspace  is  printed.  This provides a rapid display of how many packets are being
               dropped.  Only the super-user may use this option.  This can be very hard on a network and should
               be used with caution.

       -i, --interval wait
               Wait wait seconds between sending each packet.  The default is to wait  for  one  second  between
               each packet.  This option is incompatible with the -f option.

       -l, --preload preload
               If preload is specified, ping sends that many packets as fast as possible before falling into its
               normal mode of behavior.

       -n, --numeric
               Numeric output only.  No attempt will be made to lookup symbolic names for host addresses.

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

       -R, --route
               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, --ignore-routing
               Bypass the normal routing tables and send directly 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 ping a
               local host through an interface that has no route through  it  (e.g.,  after  the  interface  was
               dropped by routed(8)).

       -s, --size 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.

       -v, --verbose
               Verbose output.  ICMP packets other than ECHO_RESPONSE that are received are listed.

       --ttl N
               Set N as the packet time-to-live.

       -T, --tos num
               Set num as the packet type of service (TOS).

       -w, --timeout N
               Stop after N seconds of sending packets.

       -W, --linger N
               Number of seconds to wait for response.

       --ip-timestamp flag
               IP timestamp of type flag, which is one of "tsonly" and "tsaddr".

       -?, --help
               Display a help list.

       --usage
               Display a short usage message.

       -V, --version
               Print the program version.

       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.

       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 eight bytes large, ping uses the first eight bytes of this space to include
       a timestamp which it uses in the computation of round trip times.  If less than eight bytes  of  pad  are
       specified, 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 indicate broken hardware somewhere in the
       ping packet's path (in the network or in the hosts).

TRYING DIFFERENT DATA PATTERNS

       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.

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  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:

       •   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.

       •   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.

       •   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

       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 conditions.

SEE ALSO

       netstat(1), ifconfig(1), routed(8)

HISTORY

       The ping command appeared in 4.3BSD.

GNU Network Utilities                           February 9, 2019                                         PING(1)