Summery
ネットワークの疎通を確認する。
特定のIPアドレスやHOSTSに対してのレスポンスを簡易に計測できる。
Construction
$ ping [option] [ip/host/domain]
Option
-n : 疎通確認の回数を指定
-t : 疎通確認を無限に繰り返す（ctl + c で矯正終了）
-i : TTLを指定の値にセットする
-w : タイムアウト時間の指定（ミリ秒）
Sample
# Google.comに対しての確認
$ ping google.com
# ローカルIPでの確認
$ ping 192.168.1.1
# 5回のみの確認
$ ping -n 5 192.168.1.1
Discription
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] [-k trafficclass]
[-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]
[-k trafficclass] [-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 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.
-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 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 pack-
ets 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 0.1 second. This
option is incompatible with the -f option.
-k trafficlass
Specifies the traffic class to use for sending ICMP packets. The sup-
ported traffic classes are BK_SYS, BK, BE, RD, OAM, AV, RV, VI, VO and
CTL. By default ping uses the control traffic class (CTL).
-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 pos-
sible 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 timestamps.
-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 net-
work. 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 pack-
ets 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 pack-
ets. 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 consid-
ered 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 pro-
gram is terminated with a SIGINT, a brief summary is displayed, showing the
number of packets sent and received, and the minimum, mean, maximum, and stan-
dard 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 maxi-
mum of the round-trip times will be written to the standard error output.
This program is intended for use in network testing, measurement and manage-
ment. 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 con-
tains 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
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 situa-
tions and are rarely (if ever) a good sign, although the presence of low lev-
els 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 bro-
ken 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 prob-
lems 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. Oth-
ers 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 Bal-
listics 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 broadcast
address should only be done under very controlled conditions.
The -v option is not worth much on busy hosts.
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