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PING(8) |
FreeBSD System Manager's Manual |
PING(8) |
ping —
send ICMP or ICMPv6 ECHO_REQUEST packets to network hosts
ping |
[-4AaDdfHnoQqRrv ] [-C
pcp] [-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]
IPv4-host |
ping |
[-4AaDdfHLnoQqRrv ] [-C
pcp] [-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]
IPv4-mcast-group |
ping |
[-6AaDdEfHNnOoquvYyZ ]
[-b bufsiz]
[-c count]
[-e gateway]
[-I interface]
[-i wait]
[-k addrtype]
[-l preload]
[-m hoplimit]
[-P policy]
[-p pattern]
[-S sourceaddr]
[-s packetsize]
[-t timeout]
[-W waittime]
[IPv6-hops ...] IPv6-host |
The ping utility invoked with an IPv4 target
(IPv4-host or
IPv4-mcast-group) 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.
When invoked with an IPv6 target
(IPv6-host), it uses the ICMPv6 protocol's mandatory
ICMP6_ECHO_REQUEST datagram to elicit an ICMP6_ECHO_REPLY.
ICMP6_ECHO_REQUEST datagrams have an IPv6 header and ICMPv6 header formatted
as documented in RFC 2463.
When invoked with a hostname, the version to which the target is
resolved first is used. In that case, the options and arguments used must be
valid for the specific IP version, otherwise ping
exits with an error. If the target is resolved to both IPv4 and IPv6, the
specific IP version can be requested by -4 or
-6 options, respectively. For
backwards-compatibility, ICMPv6 can also be selected by invoking the binary
as ping6 .
-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.
-C
pcp
- Add an 802.1p Ethernet Priority Code Point when sending a packet. 0..7
uses that specific PCP, -1 uses the interface default PCP (or none).
-c
count
- Stop after sending (and receiving) count
ECHO_RESPONSE packets. If this option is not specified,
ping will operate until interrupted.
For an IPv4 target, if this option is specified in conjunction
with ping sweeps, each sweep will consist of count
packets.
-D
- Disable fragmentation.
-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.
-H
- Hostname output. Try to do a reverse DNS lookup when displaying addresses.
This is the opposite of the
-n option.
-I
iface
- For an IPv4 target, iface is an IP address
indentifying an interface from which the packets will be sent. This flag
applies only if the ping target is a multicast address.
For an IPv6 target, iface is a name of
an interface (e.g. `em0') from which the packets will be sent. This flag
applies if the ping target is a multicast address, or
link-local/site-local unicast 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
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
ttl
- For an IPv4 target, 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.
For an IPv6 target, set the IPv6 hoplimit.
-n
- Numeric output only. No attempt will be made to lookup symbolic names for
host addresses. This is the opposite of
-H , and it
is the default behavior.
-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
- Quiet output. Nothing is displayed except the summary lines at startup
time and when finished.
-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.
For IPv4, if the IP address is not one of this machine's
interface addresses, an error is returned and nothing is sent.
For IPv6, the source address must be one of the unicast
addresses of the sending node, and must be numeric.
-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.
For IPv4, only the super-user may specify values more than
default. This option cannot be used with ping sweeps.
For IPv6, you may need to specify -b
as well to extend socket buffer size.
-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.
-4
- Use IPv4 regardless of how the target is resolved.
-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.
-L
- Suppress loopback of multicast packets. This flag only applies if the ping
destination is a multicast address.
-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 .
-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.
-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)).
-T
ttl
- Set the IP Time To Live for multicasted packets. This flag only applies if
the ping destination is a multicast address.
-z
tos
- Use the specified type of service.
- IPv4-host
- hostname or IPv4 address of the final destination node.
- IPv4-mcast-group
- IPv4 multicast address of the final destination nodes.
-6
- Use IPv6 regardless of how the target is resolved.
-b
bufsiz
- Set socket buffer size.
-e
gateway
- Specifies to use gateway as the next hop to the
destination. The gateway must be a neighbor of the sending node.
-k
addrtype
- Generate ICMPv6 Node Information Node Addresses query, rather than
echo-request. addrtype must be a string constructed
of the following characters.
a
- requests unicast addresses from all of the responder's interfaces. If
the character is omitted, only those addresses which belong to the
interface which has the responder's address are requests.
c
- requests responder's IPv4-compatible and IPv4-mapped addresses.
g
- requests responder's global-scope addresses.
s
- requests responder's site-local addresses.
l
- requests responder's link-local addresses.
A
- requests responder's anycast addresses. Without this character, the
responder will return unicast addresses only. With this character, the
responder will return anycast addresses only. Note that the
specification does not specify how to get responder's anycast
addresses. This is an experimental option.
-N
- Probe node information multicast group address
(
ff02::2:ffxx:xxxx ). host
must be string hostname of the target (must not be a numeric IPv6
address). Node information multicast group will be computed based on given
host, and will be used as the final destination.
Since node information multicast group is a link-local multicast group,
outgoing interface needs to be specified by -I
option.
When specified twice, the address
(ff02::2:xxxx:xxxx ) is used instead. The former
is in RFC 4620, the latter is in an old Internet Draft
draft-ietf-ipngwg-icmp-name-lookup. Note that KAME-derived
implementations including FreeBSD use the
latter.
-O
- Generate ICMPv6 Node Information supported query types query, rather than
echo-request.
-s has no effect if
-O is specified.
-u
- By default,
ping asks the kernel to fragment
packets to fit into the minimum IPv6 MTU. The -u
option will suppress the behavior in the following two levels: when the
option is specified once, the behavior will be disabled for unicast
packets. When the option is more than once, it will be disabled for both
unicast and multicast packets.
-Y
- Same as
-y , but with old packet format based on 03
draft. This option is present for backward compatibility.
-s has no effect if -y is
specified.
-y
- Generate ICMPv6 Node Information DNS Name query, rather than echo-request.
-s has no effect if -y is
specified.
- IPv6-hops
- IPv6 addresses for intermediate nodes, which will be put into type 0
routing header.
- IPv6-host
- IPv6 address of the final destination node.
-E
- Enables transport-mode IPsec encapsulated security payload.
-Z
- Enables transport-mode IPsec authentication header.
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, maximum, and standard deviation of the round-trip times will be
written to the standard 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.
The following will send ICMPv6 echo request to
dst.foo.com .
The following will probe hostnames for all nodes on the network
link attached to wi0 interface. The address
ff02::1 is named the link-local all-node multicast
address, and the packet would reach every node on the network link.
The following will probe addresses assigned to the destination
node, dst.foo.com .
ping -6 -k agl dst.foo.com
netstat(1),
icmp(4),
icmp6(4),
inet6(4),
ip6(4),
ifconfig(8),
routed(8),
traceroute(8),
traceroute6(8)
A. Conta and
S. Deering, Internet Control
Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6)
Specification, RFC 2463,
December 1998.
Matt Crawford,
IPv6 Node Information Queries,
draft-ietf-ipngwg-icmp-name-lookups-09.txt,
May 2002, work in progress
material.
The ping utility appeared in
4.3BSD. The ping6 utility with
IPv6 support first appeared in the WIDE Hydrangea IPv6 protocol stack kit.
IPv6 and IPsec support based on the KAME Project
(http://www.kame.net/) stack was initially
integrated into FreeBSD 4.0.
The ping6 utility was merged to
ping in Google Summer of Code 2019.
The original ping utility was written by
Mike Muuss while at the US Army Ballistics Research
Laboratory.
Many Hosts and Gateways ignore the IPv4 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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