.\"	$KAME: traceroute6.8,v 1.10 2004/06/06 12:35:15 suz Exp $
.\"
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.Dd November 25, 2020
.Dt TRACEROUTE6 8
.Os
.\"
.Sh NAME
.Nm traceroute6
.Nd "print the route IPv6 packets will take to a network node"
.\"
.Sh SYNOPSIS
.Nm
.Bk -words
.Op Fl adIlnNrSTUv
.Ek
.Bk -words
.Op Fl f Ar firsthop
.Ek
.Bk -words
.Op Fl g Ar gateway
.Ek
.Bk -words
.Op Fl m Ar hoplimit
.Ek
.Bk -words
.Op Fl p Ar port
.Ek
.Bk -words
.Op Fl q Ar probes
.Ek
.Bk -words
.Op Fl s Ar src
.Ek
.Bk -words
.Op Fl t Ar tclass
.Ek
.Bk -words
.Op Fl w Ar waittime
.Ek
.Bk -words
.Op Fl A Ar as_server
.Ek
.Bk -words
.Ar target
.Op Ar datalen
.Ek
.\"
.Sh DESCRIPTION
The
.Nm
utility
uses the IPv6 protocol hop limit field to elicit an ICMPv6 TIME_EXCEEDED
response from each gateway along the path to some host.
.Pp
The only mandatory parameter is the destination host name or IPv6 address.
The default probe datagram carries 20 bytes of payload,
in addition to the IPv6 header.
The size of the payload can be specified by giving a length
(in bytes)
after the destination host name.
.Pp
Other options are:
.Bl -tag -width Ds
.It Fl a
Turn on AS# lookups for each hop encountered.
.It Fl A Ar as_server
Turn on AS# lookups and use the given server instead of the default.
.It Fl d
Debug mode.
.It Fl f Ar firsthop
Specify how many hops to skip in trace.
.It Fl g Ar gateway
Specify intermediate gateway.
Please note that
.Nm
tries to use routing headers.
.It Fl I
Use ICMP6 ECHO instead of UDP datagrams.
.It Fl l
Print both host hostnames and numeric addresses.
Normally
.Nm
prints only hostnames if
.Fl n
is not specified, and only numeric addresses if
.Fl n
is specified.
.It Fl m Ar hoplimit
Specify maximum hoplimit, up to 255.
The default is the value of the
.Va net.inet6.ip6.hlim
.Xr sysctl 8
(the same default used for TCP connections).
.It Fl n
Do not resolve numeric address to hostname.
.It Fl N
Use a packet with no upper layer header for the probes,
instead of UDP datagrams.
.It Fl p Ar port
Set SCTP/TCP/UDP port number to
.Ar port .
.It Fl q Ar probes
Set the number of probe per hop count to
.Ar probes .
.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-connected network,
an error is returned.
This option corresponds to the
.Dv SO_DONTROUTE
socket option;
it 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 a routing daemon).
.It Fl s Ar src
.Ar Src
specifies the source IPv6 address to be used.
.It Fl S
Use SCTP packets for the probes.
The size of probe packets must be a multiple of 4.
If
.Ar datalen
is up to 28, probe packets consist of a SHUTDOWN-ACK chunk possibly bundled
with a PAD chunk.
For larger probe packets, an INIT chunk is used.
.It Fl t Ar tclass
.Ar tclass
specifies the
.Em traffic class
used when sending probe packets.
The value must be a decimal integer in the range 0 to 255.
The default is 0.
.It Fl T
Use TCP segments for the probes.
.It Fl U
Use UDP datagrams for the probes.
This is the default.
.It Fl v
Be verbose.
.It Fl w Ar waittime
Specify the delay time between probes.
.El
.Pp
This program prints the route to the given destination and the round-trip
time to each gateway, in the same manner as traceroute.
.Pp
Here is a list of possible annotations after the round-trip time for each gateway:
.Bl -hang -offset indent
.It !N
Destination Unreachable - No Route to Host.
.It !P
Destination Unreachable - Administratively Prohibited.
.It !S
Destination Unreachable - Not a Neighbour.
.It !A
Destination Unreachable - Address Unreachable.
.It !H
Parameter Problem - Unrecognized Next Header Type.
.It !\&
This is printed if the hop limit is <= 1 on a port unreachable message.
This means that the packet got to the destination,
but that the reply had a hop limit that was just large enough to
allow it to get back to the source of the traceroute6.
This was more interesting in the IPv4 case,
where some IP stack bugs could be identified by this behaviour.
.El
.\"
.Sh EXIT STATUS
The
.Nm
utility will exit with 0 on success, and non-zero on errors.
.\"
.Sh SEE ALSO
.Xr ping 8 ,
.Xr traceroute 8
.\"
.Sh HISTORY
The
.Nm
utility first appeared in WIDE hydrangea IPv6 protocol stack kit.