send ICMP ECHO_REQUEST packets to network hosts
ping [ -adfLmnoqRrtv ] [ -c count ]
[ -I ip-addr ] [ -i wait ]
[-w maxwait ]
[ -l preload ]
[ -p pattern ]
[ -S src-addr ]
[ -s packetsize ]
[ -T ttl ]
-h host | 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 timeval and an arbitrary number of
``pad'' bytes used to fill out the packet. The
options are as follows:
The [!]@hop1@hop2@hop3:dest argument
defines a source route.
If it is prefixed with the ``!'' character,
it is interpreted as a strict source route.
Otherwise it is interpreted as a loose source route.
Include a bell character (ASCII 0x07)
in the output when any packet is received.
Stop after sending (and receiving) count
Set the SO_DEBUG option on the socket being
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 root may
use this option. This can be very hard on a network
and should be used with caution.
Use host as the target system.
This is equivalent to specifying host
as the last argument on the command line
and is provided as an alternate syntax
for compatibility with other systems.
When sending multicast datagrams, use the interface with address
as the originating interface.
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.
wait can be expressed in decimal,
with non-integer values supported for SCO OpenServer Release 5.0.6 and later releases.
For example, setting wait to 1.5
sends a packet every 1.5 seconds.
Only the root user
is allowed to request wait values of less than 1.0 seconds.
Causes loopback of multicast datagrams to be disabled.
If preload is specified, ping sends
that many packets as fast as possible before falling into
its normal mode of behavior.
Sends an ICMP subnet-mask request to the specified address. This
is useful for checking the configuration of a particular host.
Numeric output only: No attempt will be made to look up
symbolic names for host addresses.
Exit successfully after receiving one reply packet.
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.
Quiet output: Nothing is displayed except the summary
lines at startup time and when finished.
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.
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 (for example,
after the interface was dropped by
Use src-addr as the source address in outgoing packets.
src-addr must be one of the local machine's
interface addresses or an error is returned
and nothing is sent.
Use this option on hosts with more than one IP address
to force the source address to be something other than
the IP address on which the probe packet is sent.
-S is used for ICMP packets
whereas -I is used only for multicast addresses.
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
Set the IP time-to-live (TTL) in outgoing datagrams to
Sends an ICMP time-stamp request to the specified address. This
is useful for checking the configuration of a particular host.
Verbose output: ICMP packets other than
ECHO_RESPONSE that are received are listed.
Specify a timeout, in seconds,
before ping exits,
regardless of how many packets have been sent or received.
maxwait can be expressed in decimal.
Only the root user is allowed
to request a maxwait value of less than 0.25 seconds.
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
ping uses name resolution services
(DNS, BIND, or NIS through the
to determine the hostname for received reply packets.
Consequently, ping's results
can be affected by name service problems.
Use the -n flag to bypass name resolution
for received reply packets
if name service problems are suspected.
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
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 reports 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
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 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
can not 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 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
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 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 systems did
before the 4.3 BSD-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
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
The maximum IP header length is too small for
options like RECORD_ROUTE to be completely
useful. Not much 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.
Differences between versions
The -ahoS flags
are provided only in SCO OpenServer Release 5.0.6 and later releases;
-w only in Release 5.0.7 and later.
For releases prior to 5.0.6,
the -i wait value
must be an integer.
On SCO OpenServer Release 5.0.6 and later releases,
ping is more robust in the face of name service problems
as well as being more informative about such problems.
ping is conformant with:
RFC 792 (STD 5);
and X/Open Portability Guide, Issue 4, 1992.
© 2003 Caldera International, Inc. All rights reserved.
SCO OpenServer Release 5.0.7 -- 11 February 2003