ping - send ICMP ECHO_REQUEST to network hosts
ping [-aAbBdDfhLnOqrRUvV46] [-c
count]
[-F
flowlabel] [-i
interval]
[-I
interface] [-l
preload]
[-m
mark] [-M
pmtudisc_option]
[-N
nodeinfo_option] [-w
deadline]
[-W
timeout] [-p
pattern] [-Q
tos]
[-s
packetsize] [-S
sndbuf]
[-t
ttl] [-T
timestamp option]
[
hop...]
destination
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 then an arbitrary
number ofpadbytes used to fill out the packet.
ping works with both IPv4 and IPv6. Using only one of them explicitly can
be enforced by specifying
-4 or
-6.
ping can also send IPv6 Node Information Queries (RFC4620). Intermediate
hops may not be allowed, because IPv6 source routing was deprecated
(RFC5095).
-4
Use IPv4 only.
-6
Use IPv6 only.
-a
Audible ping.
-A
Adaptive ping. Interpacket interval adapts to round-trip
time, so that effectively not more than one (or more, if preload is set)
unanswered probe is present in the network. Minimal interval is 200msec for
not super-user. On networks with low rtt this mode is essentially equivalent
to flood mode.
-b
Allow pinging a broadcast address.
-B
Do not allow ping to change source address of
probes. The address is bound to one selected when ping starts.
-c count
Stop after sending count ECHO_REQUEST packets.
With deadline option, ping waits for count ECHO_REPLY
packets, until the timeout expires.
-d
Set the SO_DEBUG option on the socket being used.
Essentially, this socket option is not used by Linux kernel.
-D
Print timestamp (unix time + microseconds as in
gettimeofday) before each line.
-f
Flood ping. For every ECHO_REQUEST sent a period.is
printed, while for ever ECHO_REPLY received a backspace is printed. This
provides a rapid display of how many packets are being dropped. If interval is
not given, it sets interval to zero and outputs packets as fast as they come
back or one hundred times per second, whichever is more. Only the super-user
may use this option with zero interval.
-F flow label
IPv6 only. Allocate and set 20 bit flow label (in hex) on
echo request packets. If value is zero, kernel allocates random flow
label.
-h
Show help.
-i interval
Wait interval seconds between sending each packet.
The default is to wait for one second between each packet normally, or not to
wait in flood mode. Only super-user may set interval to values less than 0.2
seconds.
-I interface
interface is either an address, or an interface
name. If interface is an address, it sets source address to specified
interface address. If interface in an interface name, it sets source
interface to specified interface. NOTE: For IPv6, when doing ping to a
link-local scope address, link specification (by the '%'-notation in
destination, or by this option) can be used but it is no longer
required.
-l preload
If preload is specified, ping sends that
many packets not waiting for reply. Only the super-user may select preload
more than 3.
-L
Suppress loopback of multicast packets. This flag only
applies if the ping destination is a multicast address.
-m mark
use mark to tag the packets going out. This is
useful for variety of reasons within the kernel such as using policy routing
to select specific outbound processing.
-M pmtudisc_opt
Select Path MTU Discovery strategy.
pmtudisc_option may be either do (prohibit fragmentation, even
local one), want (do PMTU discovery, fragment locally when packet size
is large), or dont (do not set DF flag).
-N nodeinfo_option
IPv6 only. Send ICMPv6 Node Information Queries
(RFC4620), instead of Echo Request. CAP_NET_RAW capability is required.
help
Show help for NI support.
name
Queries for Node Names.
ipv6
Queries for IPv6 Addresses. There are several IPv6
specific flags.
ipv6-global
Request IPv6 global-scope addresses.
ipv6-sitelocal
Request IPv6 site-local addresses.
ipv6-linklocal
Request IPv6 link-local addresses.
ipv6-all
Request IPv6 addresses on other interfaces.
Queries for IPv4 Addresses. There is one IPv4 specific
flag.
ipv4-all
Request IPv4 addresses on other interfaces.
IPv6 subject address.
subject-ipv4=ipv4addr
IPv4 subject address.
subject-name=nodename
Subject name. If it contains more than one dot,
fully-qualified domain name is assumed.
subject-fqdn=nodename
Subject name. Fully-qualified domain name is always
assumed.
Numeric output only. No attempt will be made to lookup
symbolic names for host addresses.
-O
Report outstanding ICMP ECHO reply before sending next
packet. This is useful together with the timestamp -D to log output to
a diagnostic file and search for missing answers.
-p pattern
You may specify up to 16padbytes 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
Quiet output. Nothing is displayed except the summary
lines at startup time and when finished.
-Q tos
Set Quality of Service -related bits in ICMP datagrams.
tos can be decimal (
ping only) or hex number.
In RFC2474, these fields are interpreted as 8-bit Differentiated Services (DS),
consisting of: bits 0-1 (2 lowest bits) of separate data, and bits 2-7
(highest 6 bits) of Differentiated Services Codepoint (DSCP). In RFC2481 and
RFC3168, bits 0-1 are used for ECN.
Historically (RFC1349, obsoleted by RFC2474), these were interpreted as: bit 0
(lowest bit) for reserved (currently being redefined as congestion control),
1-4 for Type of Service and bits 5-7 (highest bits) for Precedence.
Bypass the normal routing tables and send directly to a
host on an attached interface. 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 provided the option
-I is also used.
-R
ping only. 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.
-s packetsize
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 data.
-S sndbuf
Set socket sndbuf. If not specified, it is selected to
buffer not more than one packet.
-t ttl
ping only. Set the IP Time to Live.
-T timestamp option
Set special IP timestamp options. timestamp option
may be either tsonly (only timestamps), tsandaddr (timestamps
and addresses) or tsprespec host1 [host2 [host3 [host4]]] (timestamp
prespecified hops).
-U
Print full user-to-user latency (the old behaviour).
Normally ping prints network round trip time, which can be different
f.e. due to DNS failures.
-v
Verbose output.
-V
Show version and exit.
-w deadline
Specify a timeout, in seconds, before ping exits
regardless of how many packets have been sent or received. In this case
ping does not stop after count packet are sent, it waits either
for deadline expire or until count probes are answered or for
some error notification from network.
-W timeout
Time to wait for a response, in seconds. The option
affects only timeout in absence of any responses, otherwise ping waits
for two RTTs.
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 bepinged. 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/mdev
round-trip time numbers.
Median deviation (mdev), essentially an average of how far each ping RTT is from
the mean RTT. The higher mdev is, the more variable the RTT is (over time).
With a high RTT variability, you will have speed issues with bulk transfers
(they will take longer than is strictly speaking necessary, as the variability
will eventually cause the sender to wait for ACKs) and you will have middling
to poor VoIP quality.
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. Shorter
current statistics can be obtained without termination of process with signal
SIGQUIT.
If
ping does not receive any reply packets at all it will exit with code
1. If a packet
count and
deadline are both specified, and fewer
than
count packets are received by the time the
deadline has
arrived, it will also exit with code 1. On other error it exits with code 2.
Otherwise it exits with code 0. This makes it possible to use the exit code to
see if a host is alive or not.
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 of size of struct timeval
ping uses the
beginning bytes of this space to include a timestamp which it uses in the
computation of round trip times. If the data space is shorter, 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).
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 sufficienttransitions, such as all ones or all
zeros, or a pattern right at the edge, such as almost all zeros. It isn't
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'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 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 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
canpingsome 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 Berkeley Unix 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 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
pinging 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.
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.
ip(8),
ss(8).
The
ping command appeared in 4.3BSD.
The version described here is its descendant specific to Linux.
As of version s20150815, the
ping6 binary doesn't exist anymore. It has
been merged into
ping. Creating a symlink named
ping6 pointing
to
ping will result in the same funcionality as before.
ping requires CAP_NET_RAW capability to be executed 1) if the program is
used for non-echo queries (See
-N option), or 2) if kernel does not
support non-raw ICMP sockets, or 3) if the user is not allowed to create an
ICMP echo socket. The program may be used as set-uid root.
ping is part of
iputils package.