.\"	$KAME: ping6.8,v 1.58 2003/06/20 12:00:22 itojun Exp $
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.\" $FreeBSD$
.\"
.Dd May 5, 2013
.Dt PING6 8
.Os
.Sh NAME
.Nm ping6
.Nd send
.Tn ICMPv6 ECHO_REQUEST
packets to network hosts
.Sh SYNOPSIS
.Nm
.\" without ipsec, or new ipsec
.Op Fl DdfHmnNoqrRtvwW
.\" old ipsec
.\" .Op Fl ADdEfmnNqRtvwW
.Bk -words
.Op Fl a Ar addrtype
.Ek
.Bk -words
.Op Fl b Ar bufsiz
.Ek
.Bk -words
.Op Fl c Ar count
.Ek
.Bk -words
.Op Fl g Ar gateway
.Ek
.Bk -words
.Op Fl h Ar hoplimit
.Ek
.Bk -words
.Op Fl I Ar interface
.Ek
.Bk -words
.Op Fl i Ar wait
.Ek
.Bk -words
.Op Fl l Ar preload
.Ek
.Bk -words
.\" new ipsec
.Op Fl P Ar policy
.Ek
.Bk -words
.Op Fl p Ar pattern
.Ek
.Bk -words
.Op Fl S Ar sourceaddr
.Ek
.Bk -words
.Op Fl s Ar packetsize
.Ek
.Bk -words
.Op Ar hops ...
.Ek
.Bk -words
.Ar host
.Ek
.Sh DESCRIPTION
The
.Nm
utility uses the
.Tn ICMPv6
protocol's mandatory
.Tn ICMP6_ECHO_REQUEST
datagram to elicit an
.Tn ICMP6_ECHO_REPLY
from a host or gateway.
.Tn ICMP6_ECHO_REQUEST
datagrams (``pings'') have an IPv6 header,
and
.Tn ICMPv6
header formatted as documented in RFC2463.
The options are as follows:
.Bl -tag -width Ds
.\" old ipsec
.\" .It Fl A
.\" Enables transport-mode IPsec authentication header
.\" (experimental).
.It Fl a Ar addrtype
Generate ICMPv6 Node Information Node Addresses query, rather than echo-request.
.Ar addrtype
must be a string constructed of the following characters.
.Bl -tag -width Ds -compact
.It Ic 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.
.It Ic c
requests responder's IPv4-compatible and IPv4-mapped addresses.
.It Ic g
requests responder's global-scope addresses.
.It Ic s
requests responder's site-local addresses.
.It Ic l
requests responder's link-local addresses.
.It Ic 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.
.El
.It Fl b Ar bufsiz
Set socket buffer size.
.It Fl c Ar count
Stop after sending
(and receiving)
.Ar count
.Tn ECHO_RESPONSE
packets.
.It Fl D
Disable IPv6 fragmentation.
.It Fl d
Set the
.Dv SO_DEBUG
option on the socket being used.
.\" .It Fl E
.\" Enables transport-mode IPsec encapsulated security payload
.\" (experimental).
.It Fl f
Flood ping.
Outputs packets as fast as they come back or one hundred times per second,
whichever is more.
For every
.Tn ECHO_REQUEST
sent a period
.Dq \&.
is printed, while for every
.Tn 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.
.Bf -emphasis
This can be very hard on a network and should be used with caution.
.Ef
.It Fl g Ar gateway
Specifies to use
.Ar gateway
as the next hop to the destination.
The gateway must be a neighbor of the sending node.
.It Fl H
Specifies to try reverse-lookup of IPv6 addresses.
The
.Nm
utility does not try reverse-lookup unless the option is specified.
.It Fl h Ar hoplimit
Set the IPv6 hoplimit.
.It Fl I Ar interface
Source packets with the given interface address.
This flag applies if the ping destination is a multicast address,
or link-local/site-local unicast address.
.It Fl i Ar wait
Wait
.Ar wait
seconds
.Em between sending each packet .
The default is to wait for one second between each packet.
This option is incompatible with the
.Fl f
option.
.It Fl l Ar preload
If
.Ar preload
is specified,
.Nm
sends that many packets as fast as possible before falling into its normal
mode of behavior.
Only the super-user may use this option.
.It Fl m
By default,
.Nm
asks the kernel to fragment packets to fit into the minimum IPv6 MTU.
The
.Fl m
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.
.It Fl n
Numeric output only.
No attempt will be made to lookup symbolic names from addresses in the reply.
.It Fl N
Probe node information multicast group address
.Pq Li ff02::2:ffxx:xxxx .
.Ar 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
.Ar 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
.Fl I
option.
.Pp
When specified twice, the address
.Pq Li 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
.Fx
use the latter.
.It Fl o
Exit successfully after receiving one reply packet.
.It Fl p Ar pattern
You may specify up to 16
.Dq pad
bytes to fill out the packet you send.
This is useful for diagnosing data-dependent problems in a network.
For example,
.Dq Li \-p ff
will cause the sent packet to be filled with all
ones.
.\" new ipsec
.It Fl P Ar policy
.Ar policy
specifies IPsec policy to be used for the probe.
.It Fl q
Quiet output.
Nothing is displayed except the summary lines at startup time and
when finished.
.It Fl r
Audible.
Include a bell
.Tn ( ASCII
0x07)
character in the output when any packet is received.
.It Fl R
Audible.
Output a bell
.Tn ( 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.
.It Fl S Ar sourceaddr
Specifies the source address of request packets.
The source address must be one of the unicast addresses of the sending node,
and must be numeric.
.It Fl s Ar packetsize
Specifies the number of data bytes to be sent.
The default is 56, which translates into 64
.Tn ICMP
data bytes when combined
with the 8 bytes of
.Tn ICMP
header data.
You may need to specify
.Fl b
as well to extend socket buffer size.
.It Fl t
Generate ICMPv6 Node Information supported query types query,
rather than echo-request.
.Fl s
has no effect if
.Fl t
is specified.
.It Fl v
Verbose output.
.Tn ICMP
packets other than
.Tn ECHO_RESPONSE
that are received are listed.
.It Fl w
Generate ICMPv6 Node Information DNS Name query, rather than echo-request.
.Fl s
has no effect if
.Fl w
is specified.
.It Fl W
Same as
.Fl w ,
but with old packet format based on 03 draft.
This option is present for backward compatibility.
.Fl s
has no effect if
.Fl w
is specified.
.It Ar hops
IPv6 addresses for intermediate nodes,
which will be put into type 0 routing header.
.It Ar host
IPv6 address of the final destination node.
.El
.Pp
When using
.Nm
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
.Dq 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
.Dv 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.
.Pp
If
.Nm
receives a
.Dv SIGINFO
(see the
.Cm status
argument for
.Xr 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 in the same format as the
standard completion message.
.Pp
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
.Nm
during normal operations or from automated scripts.
.\" .Sh ICMP PACKET DETAILS
.\" An IP header without options is 20 bytes.
.\" An
.\" .Tn ICMP
.\" .Tn ECHO_REQUEST
.\" packet contains an additional 8 bytes worth of
.\" .Tn ICMP
.\" header followed by an arbitrary amount of data.
.\" When a
.\" .Ar 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
.\" .Tn ICMP
.\" .Tn ECHO_REPLY
.\" will always be 8 bytes more than the requested data space
.\" (the
.\" .Tn ICMP
.\" header).
.\" .Pp
.\" If the data space is at least eight bytes large,
.\" .Nm
.\" 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.
.Sh DUPLICATE AND DAMAGED PACKETS
The
.Nm
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.
.Pp
Damaged packets are obviously serious cause for alarm and often
indicate broken hardware somewhere in the
.Nm
packet's path
(in the network or in the hosts).
.Sh 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 does not have sufficient
.Dq 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.
.Pp
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
.Fl p
option of
.Nm .
.Sh EXIT STATUS
The
.Nm
utility returns 0 on success (the host is alive),
2 if the transmission was successful but no responses were received,
any other non-zero value if the arguments are incorrect or
another error has occurred.
.Sh EXAMPLES
Normally,
.Nm
works just like
.Xr ping 8
would work; the following will send ICMPv6 echo request to
.Li dst.foo.com .
.Bd -literal -offset indent
ping6 -n dst.foo.com
.Ed
.Pp
The following will probe hostnames for all nodes on the network link attached to
.Li wi0
interface.
The address
.Li ff02::1
is named the link-local all-node multicast address, and the packet would
reach every node on the network link.
.Bd -literal -offset indent
ping6 -w ff02::1%wi0
.Ed
.Pp
The following will probe addresses assigned to the destination node,
.Li dst.foo.com .
.Bd -literal -offset indent
ping6 -a agl dst.foo.com
.Ed
.Sh SEE ALSO
.Xr netstat 1 ,
.Xr icmp6 4 ,
.Xr inet6 4 ,
.Xr ip6 4 ,
.Xr ifconfig 8 ,
.Xr ping 8 ,
.Xr routed 8 ,
.Xr traceroute 8 ,
.Xr traceroute6 8
.Rs
.%A A. Conta
.%A S. Deering
.%T "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification"
.%N RFC2463
.%D December 1998
.Re
.Rs
.%A Matt Crawford
.%T "IPv6 Node Information Queries"
.%N draft-ietf-ipngwg-icmp-name-lookups-09.txt
.%D May 2002
.%O work in progress material
.Re
.Sh HISTORY
The
.Xr ping 8
utility appeared in
.Bx 4.3 .
The
.Nm
utility with IPv6 support first appeared in the WIDE Hydrangea IPv6
protocol stack kit.
.Pp
IPv6 and IPsec support based on the KAME Project
.Pq Pa http://www.kame.net/
stack was initially integrated into
.Fx 4.0 .
.Sh BUGS
The
.Nm
utility
is intentionally separate from
.Xr ping 8 .
.Pp
There have been many discussions on why we separate
.Nm
and
.Xr ping 8 .
Some people argued that it would be more convenient to uniform the
ping command for both IPv4 and IPv6.
The followings are an answer to the request.
.Pp
From a developer's point of view:
since the underling raw sockets API is totally different between IPv4
and IPv6, we would end up having two types of code base.
There would actually be less benefit to uniform the two commands
into a single command from the developer's standpoint.
.Pp
From an operator's point of view: unlike ordinary network applications
like remote login tools, we are usually aware of address family when using
network management tools.
We do not just want to know the reachability to the host, but want to know the
reachability to the host via a particular network protocol such as
IPv6.
Thus, even if we had a unified
.Xr ping 8
command for both IPv4 and IPv6, we would usually type a
.Fl 6
or
.Fl 4
option (or something like those) to specify the particular address family.
This essentially means that we have two different commands.