allows you to start tracing at a hop number other than 1. Submitted by: Stefan `Sec` Zehl <sec@42.org>
334 lines
11 KiB
Groff
334 lines
11 KiB
Groff
.\" Copyright (c) 1989, 1995, 1996
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms are permitted
|
|
.\" provided that the above copyright notice and this paragraph are
|
|
.\" duplicated in all such forms and that any documentation,
|
|
.\" advertising materials, and other materials related to such
|
|
.\" distribution and use acknowledge that the software was developed
|
|
.\" by the University of California, Berkeley. The name of the
|
|
.\" University may not be used to endorse or promote products derived
|
|
.\" from this software without specific prior written permission.
|
|
.\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
|
|
.\" IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
|
|
.\" WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
|
|
.\"
|
|
.\" $Header: /home/ncvs/src/contrib/traceroute/traceroute.8,v 1.4 1999/05/06 03:23:23 archie Exp $
|
|
.\"
|
|
.TH TRACEROUTE 8 "27 September 1996"
|
|
.UC 6
|
|
.SH NAME
|
|
traceroute \- print the route packets take to network host
|
|
.SH SYNOPSIS
|
|
.. while ((op = getopt(argc, argv, "dnrvg:M:m:P:p:q:s:t:w:")) != EOF)
|
|
.na
|
|
.B traceroute
|
|
[
|
|
.B \-Sdnrv
|
|
] [
|
|
.B \-g
|
|
.I gw_host
|
|
] [
|
|
.B \-M
|
|
.I min_ttl
|
|
]
|
|
.br
|
|
.ti +8
|
|
[
|
|
.B \-m
|
|
.I max_ttl
|
|
] [
|
|
.B \-P
|
|
.I proto
|
|
] [
|
|
.B \-p
|
|
.I port
|
|
]
|
|
.br
|
|
.ti +8
|
|
[
|
|
.B \-q
|
|
.I nqueries
|
|
] [
|
|
.B \-s
|
|
.I src_addr
|
|
] [
|
|
.B \-t
|
|
.I tos
|
|
]
|
|
.br
|
|
.ti +8
|
|
[
|
|
.B \-w
|
|
.I waittime
|
|
]
|
|
.I host
|
|
[
|
|
.I packetlen
|
|
]
|
|
.ad
|
|
.SH DESCRIPTION
|
|
The Internet is a large and complex aggregation of
|
|
network hardware, connected together by gateways.
|
|
Tracking the route one's packets follow (or finding the miscreant
|
|
gateway that's discarding your packets) can be difficult.
|
|
.I Traceroute
|
|
utilizes the IP protocol `time to live' field and attempts to elicit an
|
|
ICMP TIME_EXCEEDED response from each gateway along the path to some
|
|
host.
|
|
.PP
|
|
The only mandatory parameter is the destination host name or IP number.
|
|
The default probe datagram length is 40 bytes, but this may be increased
|
|
by specifying a packet length (in bytes) after the destination host
|
|
name.
|
|
.PP
|
|
Other options are:
|
|
.TP
|
|
.B \-S
|
|
Print a summary of how many probes were not answered for each hop.
|
|
.TP
|
|
.B \-g
|
|
Specify a loose source route gateway (8 maximum).
|
|
.TP
|
|
.B \-M
|
|
Set the initial time-to-live value used in outgoing probe packets.
|
|
The default is 1, i.e., start with the first hop.
|
|
.TP
|
|
.B \-m
|
|
Set the max time-to-live (max number of hops) used in outgoing probe
|
|
packets. The default is 30 hops (the same default used for TCP
|
|
connections).
|
|
.TP
|
|
.B \-n
|
|
Print hop addresses numerically rather than symbolically and numerically
|
|
(saves a nameserver address-to-name lookup for each gateway found on the
|
|
path).
|
|
.TP
|
|
.B \-P
|
|
Send packets of specified IP protocol. The currently supported protocols
|
|
are: UDP, TCP and GRE. Other protocols may also be specified (either by
|
|
name or by number), though
|
|
.I traceroute
|
|
does not implement any special knowledge of their packet formats. This
|
|
option is useful for determining which router along a path may be
|
|
blocking packets based on IP protocol number. But see BUGS below.
|
|
.TP
|
|
.B \-p
|
|
Protocol specific. For UDP and TCP, sets
|
|
the base port number used in probes (default is 33434).
|
|
Traceroute hopes that nothing is listening on UDP ports
|
|
.I base
|
|
to
|
|
.I base + nhops - 1
|
|
at the destination host (so an ICMP PORT_UNREACHABLE message will
|
|
be returned to terminate the route tracing). If something is
|
|
listening on a port in the default range, this option can be used
|
|
to pick an unused port range.
|
|
.TP
|
|
.B \-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
|
|
.IR routed (8C)).
|
|
.TP
|
|
.B \-s
|
|
Use the following IP address (which must be given as an IP number, not
|
|
a hostname) as the source address in outgoing probe 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. If the IP address
|
|
is not one of this machine's interface addresses, an error is
|
|
returned and nothing is sent.
|
|
.TP
|
|
.B \-t
|
|
Set the
|
|
.I type-of-service
|
|
in probe packets to the following value (default zero). The value must be
|
|
a decimal integer in the range 0 to 255. This option can be used to
|
|
see if different types-of-service result in different paths. (If you
|
|
are not running 4.4bsd, this may be academic since the normal network
|
|
services like telnet and ftp don't let you control the TOS).
|
|
Not all values of TOS are legal or
|
|
meaningful \- see the IP spec for definitions. Useful values are
|
|
probably `-t 16' (low delay) and `-t 8' (high throughput).
|
|
.TP
|
|
.B \-v
|
|
Verbose output. Received ICMP packets other than TIME_EXCEEDED and
|
|
UNREACHABLEs are listed.
|
|
.TP
|
|
.B \-w
|
|
Set the time (in seconds) to wait for a response to a probe (default 5
|
|
sec.).
|
|
.PP
|
|
This program attempts to trace the route an IP packet would follow to some
|
|
internet host by launching UDP probe
|
|
packets with a small ttl (time to live) then listening for an
|
|
ICMP "time exceeded" reply from a gateway. We start our probes
|
|
with a ttl of one and increase by one until we get an ICMP "port
|
|
unreachable" (which means we got to "host") or hit a max (which
|
|
defaults to 30 hops & can be changed with the \-m flag). Three
|
|
probes (change with \-q flag) are sent at each ttl setting and a
|
|
line is printed showing the ttl, address of the gateway and
|
|
round trip time of each probe. If the probe answers come from
|
|
different gateways, the address of each responding system will
|
|
be printed. If there is no response within a 5 sec. timeout
|
|
interval (changed with the \-w flag), a "*" is printed for that
|
|
probe.
|
|
.PP
|
|
We don't want the destination
|
|
host to process the UDP probe packets so the destination port is set to an
|
|
unlikely value (if some clod on the destination is using that
|
|
value, it can be changed with the \-p flag).
|
|
.PP
|
|
A sample use and output might be:
|
|
|
|
.RS
|
|
.nf
|
|
[yak 71]% traceroute nis.nsf.net.
|
|
traceroute to nis.nsf.net (35.1.1.48), 30 hops max, 38 byte packet
|
|
1 helios.ee.lbl.gov (128.3.112.1) 19 ms 19 ms 0 ms
|
|
2 lilac-dmc.Berkeley.EDU (128.32.216.1) 39 ms 39 ms 19 ms
|
|
3 lilac-dmc.Berkeley.EDU (128.32.216.1) 39 ms 39 ms 19 ms
|
|
4 ccngw-ner-cc.Berkeley.EDU (128.32.136.23) 39 ms 40 ms 39 ms
|
|
5 ccn-nerif22.Berkeley.EDU (128.32.168.22) 39 ms 39 ms 39 ms
|
|
6 128.32.197.4 (128.32.197.4) 40 ms 59 ms 59 ms
|
|
7 131.119.2.5 (131.119.2.5) 59 ms 59 ms 59 ms
|
|
8 129.140.70.13 (129.140.70.13) 99 ms 99 ms 80 ms
|
|
9 129.140.71.6 (129.140.71.6) 139 ms 239 ms 319 ms
|
|
10 129.140.81.7 (129.140.81.7) 220 ms 199 ms 199 ms
|
|
11 nic.merit.edu (35.1.1.48) 239 ms 239 ms 239 ms
|
|
.fi
|
|
.RE
|
|
|
|
Note that lines 2 & 3 are the same. This is due to a buggy
|
|
kernel on the 2nd hop system \- lbl-csam.arpa \- that forwards
|
|
packets with a zero ttl (a bug in the distributed version
|
|
of 4.3BSD). Note that you have to guess what path
|
|
the packets are taking cross-country since the NSFNet (129.140)
|
|
doesn't supply address-to-name translations for its NSSes.
|
|
.PP
|
|
A more interesting example is:
|
|
|
|
.RS
|
|
.nf
|
|
[yak 72]% traceroute allspice.lcs.mit.edu.
|
|
traceroute to allspice.lcs.mit.edu (18.26.0.115), 30 hops max
|
|
1 helios.ee.lbl.gov (128.3.112.1) 0 ms 0 ms 0 ms
|
|
2 lilac-dmc.Berkeley.EDU (128.32.216.1) 19 ms 19 ms 19 ms
|
|
3 lilac-dmc.Berkeley.EDU (128.32.216.1) 39 ms 19 ms 19 ms
|
|
4 ccngw-ner-cc.Berkeley.EDU (128.32.136.23) 19 ms 39 ms 39 ms
|
|
5 ccn-nerif22.Berkeley.EDU (128.32.168.22) 20 ms 39 ms 39 ms
|
|
6 128.32.197.4 (128.32.197.4) 59 ms 119 ms 39 ms
|
|
7 131.119.2.5 (131.119.2.5) 59 ms 59 ms 39 ms
|
|
8 129.140.70.13 (129.140.70.13) 80 ms 79 ms 99 ms
|
|
9 129.140.71.6 (129.140.71.6) 139 ms 139 ms 159 ms
|
|
10 129.140.81.7 (129.140.81.7) 199 ms 180 ms 300 ms
|
|
11 129.140.72.17 (129.140.72.17) 300 ms 239 ms 239 ms
|
|
12 * * *
|
|
13 128.121.54.72 (128.121.54.72) 259 ms 499 ms 279 ms
|
|
14 * * *
|
|
15 * * *
|
|
16 * * *
|
|
17 * * *
|
|
18 ALLSPICE.LCS.MIT.EDU (18.26.0.115) 339 ms 279 ms 279 ms
|
|
.fi
|
|
.RE
|
|
|
|
Note that the gateways 12, 14, 15, 16 & 17 hops away
|
|
either don't send ICMP "time exceeded" messages or send them
|
|
with a ttl too small to reach us. 14 \- 17 are running the
|
|
MIT C Gateway code that doesn't send "time exceeded"s. God
|
|
only knows what's going on with 12.
|
|
.PP
|
|
The silent gateway 12 in the above may be the result of a bug in
|
|
the 4.[23]BSD network code (and its derivatives): 4.x (x <= 3)
|
|
sends an unreachable message using whatever ttl remains in the
|
|
original datagram. Since, for gateways, the remaining ttl is
|
|
zero, the ICMP "time exceeded" is guaranteed to not make it back
|
|
to us. The behavior of this bug is slightly more interesting
|
|
when it appears on the destination system:
|
|
|
|
.RS
|
|
.nf
|
|
1 helios.ee.lbl.gov (128.3.112.1) 0 ms 0 ms 0 ms
|
|
2 lilac-dmc.Berkeley.EDU (128.32.216.1) 39 ms 19 ms 39 ms
|
|
3 lilac-dmc.Berkeley.EDU (128.32.216.1) 19 ms 39 ms 19 ms
|
|
4 ccngw-ner-cc.Berkeley.EDU (128.32.136.23) 39 ms 40 ms 19 ms
|
|
5 ccn-nerif35.Berkeley.EDU (128.32.168.35) 39 ms 39 ms 39 ms
|
|
6 csgw.Berkeley.EDU (128.32.133.254) 39 ms 59 ms 39 ms
|
|
7 * * *
|
|
8 * * *
|
|
9 * * *
|
|
10 * * *
|
|
11 * * *
|
|
12 * * *
|
|
13 rip.Berkeley.EDU (128.32.131.22) 59 ms ! 39 ms ! 39 ms !
|
|
.fi
|
|
.RE
|
|
|
|
Notice that there are 12 "gateways" (13 is the final
|
|
destination) and exactly the last half of them are "missing".
|
|
What's really happening is that rip (a Sun-3 running Sun OS3.5)
|
|
is using the ttl from our arriving datagram as the ttl in its
|
|
ICMP reply. So, the reply will time out on the return path
|
|
(with no notice sent to anyone since ICMP's aren't sent for
|
|
ICMP's) until we probe with a ttl that's at least twice the path
|
|
length. I.e., rip is really only 7 hops away. A reply that
|
|
returns with a ttl of 1 is a clue this problem exists.
|
|
Traceroute prints a "!" after the time if the ttl is <= 1.
|
|
Since vendors ship a lot of obsolete (DEC's Ultrix, Sun 3.x) or
|
|
non-standard (HPUX) software, expect to see this problem
|
|
frequently and/or take care picking the target host of your
|
|
probes.
|
|
|
|
Other possible annotations after the time are
|
|
.BR !H ,
|
|
.BR !N ,
|
|
or
|
|
.B !P
|
|
(got a host, network or protocol unreachable, respectively),
|
|
.B !S
|
|
or
|
|
.B !F
|
|
(source route failed or fragmentation needed \- neither of these should
|
|
ever occur and the associated gateway is busted if you see one),
|
|
.B !X
|
|
(communication administratively prohibited), or
|
|
.B !<N>
|
|
(ICMP unreachable code N).
|
|
If almost all the probes result in some kind of unreachable, traceroute
|
|
will give up and exit.
|
|
.PP
|
|
This program is intended for use in network testing, measurement
|
|
and management.
|
|
It should be used primarily for manual fault isolation.
|
|
Because of the load it could impose on the network, it is unwise to use
|
|
.I traceroute
|
|
during normal operations or from automated scripts.
|
|
.SH SEE ALSO
|
|
netstat(1), ping(8)
|
|
.SH AUTHOR
|
|
Implemented by Van Jacobson from a suggestion by Steve Deering. Debugged
|
|
by a cast of thousands with particularly cogent suggestions or fixes from
|
|
C. Philip Wood, Tim Seaver and Ken Adelman.
|
|
.LP
|
|
The current version is available via anonymous ftp:
|
|
.LP
|
|
.RS
|
|
.I ftp://ftp.ee.lbl.gov/traceroute.tar.Z
|
|
.RE
|
|
.SH BUGS
|
|
When using protocols other than UDP, functionality is reduced.
|
|
In particular, the last packet will often appear to be lost, because
|
|
even though it reaches the destination host, there's no way to know
|
|
that because no ICMP message is sent back.
|
|
In the TCP case,
|
|
.I traceroute
|
|
should listen for a RST from the destination host (or an intermediate
|
|
router that's filtering packets), but this is not implemented yet.
|
|
.PP
|
|
Please send bug reports to traceroute@ee.lbl.gov.
|