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BSD 2.11 - man page for traceroute (bsd section 8)

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TRACEROUTE(8)									    TRACEROUTE(8)

NAME
       traceroute - print the route packets take to network host

SYNOPSIS
       traceroute  [  -m max_ttl ] [ -n ] [ -p port ] [ -q nqueries ] [ -r ] [ -s src_addr ] [ -t
       tos ] [ -w ] [ -w waittime ] host [ packetsize ]

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.  Traceroute  utilizes	the  IP  protocol
       `time to live' field and attempts to elicit an ICMP TIME_EXCEEDED response from each gate-
       way along the path to some host.

       The only mandatory parameter is the destination host name or IP number.	The default probe
       datagram  length  is  38  bytes, but this may be increased by specifying a packet size (in
       bytes) after the destination host name.

       Other options are:

       -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).

       -n     Print  hop  addresses numerically rather than symbolically and numerically (saves a
	      nameserver address-to-name lookup for each gateway found on the path).

       -p     Set the base UDP port number used in probes (default is 33434).	Traceroute  hopes
	      that nothing is listening on UDP ports base to base+nhops-1 at the destination host
	      (so an ICMP PORT_UNREACHABLE message will be returned to terminate the route  trac-
	      ing).  If something is listening on a port in the default range, this option can be
	      used to pick an unused port range.

       -r     Bypass the normal routing tables and send directly to a host on  an  attached  net-
	      work.   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(8C)).

       -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.

       -t     Set the 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  mean-
	      ingful  - see the IP spec for definitions.  Useful values are probably `-t 16' (low
	      delay) and `-t 8' (high throughput).

       -v     Verbose output.  Received ICMP packets other than  TIME_EXCEEDED	and  UNREACHABLEs
	      are listed.

       -w     Set the time (in seconds) to wait for a response to a probe (default 3 sec.).

       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  3  sec.  timeout interval (changed with the -w flag), a "*" is printed for that
       probe.

       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).

       A sample use and output might be:

	      [yak 71]% traceroute nis.nsf.net.
	      traceroute to nis.nsf.net (35.1.1.48), 30 hops max, 56 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

       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.

       A more interesting example is:

	      [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

       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.

       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:

	       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 !

       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 prob-
       lem 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 !H, !N, !P (got a host, network or  protocol
       unreachable,  respectively),  !S or !F (source route failed or fragmentation needed - nei-
       ther of these should ever occur and the associated gateway is busted if you see one).   If
       almost  all  the  probes  result  in some kind of unreachable, traceroute will give up and
       exit.

       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 traceroute during normal operations or from	automated
       scripts.

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.

SEE ALSO
       netstat(1), ping(8)

4.3 Berkeley Distribution		February 28, 1989			    TRACEROUTE(8)
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