| PING(8) | System Manager's Manual | PING(8) | 
ping —
| ping | [ -aCDdfLnoPQqRrv] [-ccount] [-Epolicy] [-ggateway] [-hhost] [-Isrcaddr] [-iinterval] [-lpreload] [-ppattern] [-spacketsize] [-Tttl] [-ttos] [-wdeadline] host | 
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
  timespec” and then an arbitrary number of ``pad'' bytes used to fill
  out the packet. The options are as follows:
-a-C-c
    count-DDon't Fragment bit in the IP header. This
      can be used to determine the path MTU.-dSO_DEBUG option on the socket being
    used.-E
    policy-P in
      KAME/FreeBSD and KAME/BSDI (as -P was already
      occupied in NetBSD).-f-g
    gateway-h
    host-I
    srcaddr-i
    interval-L-l
    preloadping sends that many packets as fast as possible
      before falling into its normal mode of behavior. Only the super-user may
      use this option.-n-o-P-p
    pattern-p ff” will cause the sent
      packet to be filled with all ones.-Q-q-R-g option. This is why it was necessary to invent
      traceroute(8). Many
      hosts ignore or discard this option.-r-s
    packetsize-T
    ttl-t
    tos-v-w
    deadlineWhen 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. The summary information can be displayed while
    ping is running by sending it a
    SIGINFO signal (see the “status”
    argument for stty(1) for more
    information).
ping continually sends one datagram per
    second, and prints one line of output for every ECHO_RESPONSE returned. On a
    trusted system with IP Security Options enabled, if the network idiom is not
    MONO, ping also prints a second line containing the
    hexadecimal representation of the IP security option in the ECHO_RESPONSE.
    If the -c count option is given, only that number of
    requests is sent. No output is produced if there is no response. 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 an interrupt (SIGINT), a brief summary is displayed. When not using the
    -f (flood) option, the first interrupt, usually
    generated by control-C or DEL, causes ping to wait
    for its outstanding requests to return. It will wait no longer than the
    longest round trip time encountered by previous, successful pings. The
    second interrupt stops ping immediately.
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.
If the data space is at least sizeof(struct
    timespec) (16) large, ping uses the first
    sizeof(struct timespec) bytes to include a timestamp
    to compute round trip times. Otherwise if the data space is at least eight
    bytes large (or the -C flag is specified),
    ping uses the first eight bytes of this space to
    include a timestamp to compute round trip times. If there are not enough
    bytes of pad 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
    packet's path (in the network or in the hosts).
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.
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 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:
pinging host.ping returns 0 on success (the host is alive), and
  non-zero if the arguments are incorrect or the host is not responding.
ping command appeared in
  4.3BSD. IPsec support was added by WIDE/KAME project.
The ping program has evolved differently
    under different operating systems, and in some cases the same flag performs
    a different function under different operating systems. The
    -t flag conflicts with
    FreeBSD. The -a,
    -c, -I,
    -i, -l,
    -P, -p,
    -s, and -t flags conflict
    with Solaris.
Some 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.
| September 10, 2011 | NetBSD 10.1 |