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.\"     $NetBSD: ping6.8,v 1.2 1999/07/04 02:46:28 itojun Exp $
.\"     KAME Id: ping6.8,v 1.1.2.5.4.1.4.1 1999/03/21 15:57:58 jinmei Exp
.\"
.Dd May 17, 1998
.Dt PING6 8
.Os
.Sh NAME
.Nm ping6
.Nd send
.Tn ICMPv6 ECHO_REQUEST
packets to network hosts
.Sh SYNOPSIS
.Nm
.Op Fl AdEfnqRrvw
.Op Fl a Ar addrtype
.Op Fl b Ar bufsiz
.Op Fl c Ar count
.Op Fl h Ar hoplimit
.Op Fl I Ar interface
.Op Fl i Ar wait
.Op Fl l Ar preload
.Op Fl p Ar pattern
.Op Fl s Ar packetsize
.Ar host
.Sh DESCRIPTION
.Bl -tag -width Ds
.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 charaters.
.Bl -tag -width Ds -compact
.It Ic a
requires all the responder's unicast addresses. If the charater is ommited,
only those addresses which belong to the interface which has the
responder's address are required.
.It Ic g
requires responder's global-scope addresses.
.It Ic s
requires responder's site-local addresses.
.It Ic l
requires responder's link-local addresses.
.El
.It Fl b Ar bufsiz
Set socket buffer size.
.It Fl c Ar count
Stop after sending
.Pq and receiving
.Ar count
.Tn ECHO_RESPONSE
packets.
.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 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 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.
.It Fl n
Numeric output only.
No attempt will be made to lookup symbolic names for host addresses.
.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.
.Fl Q
flag, 
.Nm
prints out any ICMP error messages caused by its own ECHO_REQUEST
messages.
.It Fl q
Quiet output.
Nothing is displayed except the summary lines at startup time and
when finished.
.It Fl R
Record route.
Includes the
.Tn RECORD_ROUTE
option in the
.Tn 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
.Xr traceroute 8
command is usually better at determining the route packets take to a
particular destination.
Many hosts ignore or discard the
.Tn RECORD_ROUTE
option.
.It Fl 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 
.Po
e.g., after the interface was dropped by
.Xr routed 8
.Pc .
.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.
.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 FQDN query, rather than echo-request.
.It Fl W
Same as
.Fl w.
This option was remained for backward compatibility.
.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
.Pq 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, maximum, mean, and standard deviation of
the round-trip times.
.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
.\" .Pq 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
.\" .Pq 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
.Nm Ping6
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
.Pq 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 ping
packet's path
.Pq 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 Ns .
.Sh RETURN VALUES
The
.Nm
command returns an exit status of zero if at least one response was
heard from the specified
.Ar host ;
a status of two if the transmission was successful but no responses
were received; or another value
.Pq from Aq Pa sysexits.h
if an error occurred.
.Sh SEE ALSO
.Xr netstat 1 ,
.Xr ifconfig 8 ,
.Xr routed 8 ,
.Xr ping 8 ,
.Xr traceroute 8 ,
.Xr traceroute6 8
.Sh HISTORY
The
.Nm ping
command appeared in
.Bx 4.3 .
.Nm Ping6
command with IPv6 support first appeared in WIDE Hydrangea IPv6 protocol stack
kit.
.\" .Sh BUGS
.\" (to be written)