ping
—
send ICMP ECHO_REQUEST packets to network hosts
ping |
[ -AaDdfnoQqRrv ]
[-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 ]
[-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 |
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 transmissions, further missing
packets cause a bell only if the maximum 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.
-c
count
- Stop after sending (and receiving) count
ECHO_RESPONSE packets. If this option is not specified,
ping
will operate until interrupted. 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 network 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 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
and net.inet.icmp.maskfake if you want to
override the netmask in the response. For
time
, print the origination, reception
and transmission timestamps. Set the
net.inet.icmp.tstamprepl MIB variable to
enable or disable
ICMP_TSTAMPREPLY
.
-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 overbearing. Without the
-Q
flag,
ping
prints out any ICMP error messages
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. Only the super-user may specify values more than default.
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 calculation, although the round trip time of these packets is used
in calculating 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 management.
Because of the load it can impose on the network, it is unwise to use
ping
during normal operations or from
automated scripts.
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.
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).
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
.
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:
- 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.
- 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
ping
ing
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.
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>
.
netstat(1),
icmp(4),
ifconfig(8),
routed(8),
traceroute(8)
The
ping
utility appeared in
4.3BSD.
The original
ping
utility was written by
Mike Muuss while at the US Army Ballistics
Research Laboratory.
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 broadcast
address should only be done under very controlled conditions.
The
-v
option is not worth much on busy
hosts.