ping(8) BSD System Manager's Manual ping(8)
NAME
ping -- send ICMP ECHO_REQUEST packets to network hosts
SYNOPSIS
ping [-AaCDdfnoQqRrv] [-b boundif] [-c count] [-G sweepmaxsize]
[-g sweepminsize] [-h sweepincrsize] [-i wait] [-l preload]
[-M mask | time] [-m ttl] [-P policy] [-p pattern] [-S src_addr]
[-s packetsize] [-t timeout] [-W waittime] [-z tos] host
ping [-AaDdfLnoQqRrv] [-b boundif] [-c count] [-I iface] [-i wait]
[-l preload] [-M mask | time] [-m ttl] [-P policy] [-p pattern]
[-S src_addr] [-s packetsize] [-T ttl] [-t timeout] [-W waittime]
[-z tos] mcast-group
DESCRIPTION
The ping utility 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. The options are as follows:
-A Audible. Output a bell (ASCII 0x07) character when no packet is
received before the next packet is transmitted. To cater for
round-trip times that are longer than the interval between trans-
missions, further missing packets cause a bell only if the maxi-
mum number of unreceived packets has increased.
-a Audible. Include a bell (ASCII 0x07) character in the output
when any packet is received. This option is ignored if other
format options are present.
-b boundif
Bind the socket to interface boundif for sending.
-C Prohibit the socket from using the cellular network interface.
-c count
Stop after sending (and receiving) count ECHO_RESPONSE packets.
If this option is not specified, ping will operate until inter-
rupted. If this option is specified in conjunction with ping
sweeps, each sweep will consist of count packets.
-D Set the Don't Fragment bit.
-d Set the SO_DEBUG option on the socket being used.
-f 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 net-
work and should be used with caution.
-G sweepmaxsize
Specify the maximum size of ICMP payload when sending sweeping
pings. This option is required for ping sweeps.
-g sweepminsize
Specify the size of ICMP payload to start with when sending
sweeping pings. The default value is 0.
-h sweepincrsize
Specify the number of bytes to increment the size of ICMP payload
after each sweep when sending sweeping pings. The default value
is 1.
-I iface
Source multicast packets with the given interface address. This
flag only applies if the ping destination is a multicast address.
-i wait
Wait wait seconds between sending each packet. The default is to
wait for one second between each packet. The wait time may be
fractional, but only the super-user may specify values less than
0.1 second. This option is incompatible with the -f option.
-L Suppress loopback of multicast packets. This flag only applies
if the ping destination is a multicast address.
-l preload
If preload is specified, ping sends that many packets as fast as
possible before falling into its normal mode of behavior. Only
the super-user may use this option.
-M mask | time
Use ICMP_MASKREQ or ICMP_TSTAMP instead of ICMP_ECHO. For mask,
print the netmask of the remote machine. Set the
net.inet.icmp.maskrepl MIB variable to enable ICMP_MASKREPLY.
For time, print the origination, reception and transmission time-
stamps.
-m ttl Set the IP Time To Live for outgoing packets. If not specified,
the kernel uses the value of the net.inet.ip.ttl MIB variable.
-n Numeric output only. No attempt will be made to lookup symbolic
names for host addresses.
-o Exit successfully after receiving one reply packet.
-P policy
policy specifies IPsec policy for the ping session. For details
please refer to ipsec(4) and ipsec_set_policy(3).
-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 Somewhat quiet output. Don't display ICMP error messages that
are in response to our query messages. Originally, the -v flag
was required to display such errors, but -v displays all ICMP
error messages. On a busy machine, this output can be overbear-
ing. Without the -Q flag, ping prints out any ICMP error mes-
sages caused by its own ECHO_REQUEST messages.
-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; the traceroute(8) command is usually better at
determining the route packets take to a particular destination.
If more routes come back than should, such as due to an illegal
spoofed packet, ping will print the route list and then truncate
it at the correct spot. Many hosts ignore or discard the
RECORD_ROUTE option.
-r 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 src_addr
Use the following IP address as the source address in outgoing
packets. On hosts with more than one IP address, this option can
be used to force the source address to be something other than
the IP address of the interface the probe packet is sent on. If
the IP address is not one of this machine's interface addresses,
an error is returned and nothing is sent.
-s packetsize
Specify 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. This option cannot be used with ping
sweeps.
-T ttl Set the IP Time To Live for multicasted packets. This flag only
applies if the ping destination is a multicast address.
-t timeout
Specify a timeout, in seconds, before ping exits regardless of
how many packets have been received.
-v Verbose output. ICMP packets other than ECHO_RESPONSE that are
received are listed.
-W waittime
Time in milliseconds to wait for a reply for each packet sent.
If a reply arrives later, the packet is not printed as replied,
but considered as replied when calculating statistics.
-z tos Use the specified type of service.
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 calcula-
tion, although the round trip time of these packets is used in calculat-
ing the round-trip time statistics. 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, showing the number of packets sent
and received, and the minimum, mean, maximum, and standard deviation of
the round-trip times.
If ping receives a SIGINFO (see the status argument for stty(1)) signal,
the current number of packets sent and received, and the minimum, mean,
and maximum of the round-trip times will be written to the standard error
output.
This program is intended for use in network testing, measurement and man-
agement. 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 arbi-
trary 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
The ping utility will report duplicate and damaged packets. Duplicate
packets should never occur when pinging a unicast address, 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.
Duplicates are expected when pinging a broadcast or multicast address,
since they are not really duplicates but replies from different hosts to
the same request.
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 does not have sufficient ``transitions'',
such as all ones or all zeros, or a pattern right at the edge, such as
almost all zeros. It is not 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 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.
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 recommends setting the TTL field for IP packets
to 64, 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:
o Not change it; this is what BSD 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.
o Set it to 255; this is what current BSD 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.
o 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.
EXIT STATUS
The ping utility exits with one of the following values:
0 At least one response was heard from the specified host.
2 The transmission was successful but no responses were received.
any other value
An error occurred. These values are defined in <sysexits.h>.
SEE ALSO
netstat(1), ifconfig(8), routed(8), traceroute(8), ping6(8)
HISTORY
The ping utility appeared in 4.3BSD.
AUTHORS
The original ping utility was written by Mike Muuss while at the US Army
Ballistics Research Laboratory.
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 can be done about this,
however.
Flood pinging is not recommended in general, and flood pinging the broad-
cast address should only be done under very controlled conditions.
The -v option is not worth much on busy hosts.
BSD March 29, 2013 BSD
Mac OS X 10.9 - Generated Fri Oct 18 06:31:53 CDT 2013