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RedHat 9 (Linux i386) - man page for tracepath (redhat section 8)

TRACEPATH(8)			 System Manager's Manual: iputils		     TRACEPATH(8)

NAME
       tracepath, tracepath6 - traces path to a network host discovering MTU along this path

SYNOPSIS
       tracepath destination [ port]

DESCRIPTION
       It  traces  path to destination discovering MTU along this path.  It uses UDP port port or
       some random port.  It is similar to traceroute, only does not not require superuser privi-
       leges and has no fancy options.

       tracepath6 is good replacement for traceroute6 and classic example of application of Linux
       error queues.  The situation with tracepath is worse, because commercial IP routers do not
       return  enough  information  in	icmp error messages.  Probably, it will change, when they
       will be updated.  For now it uses Van Jacobson's trick, sweeping a range of UDP	ports  to
       maintain trace history.

OUTPUT
       root@mops:~ # tracepath6 3ffe:2400:0:109::2
	1?: [LOCALHOST] 			     pmtu 1500
	1:  dust.inr.ac.ru		     0.411ms
	2:  dust.inr.ac.ru	  asymm  1   0.390ms pmtu 1480
	2:  3ffe:2400:0:109::2		     463.514ms reached
	    Resume: pmtu 1480 hops 2 back 2

       The  first  column  shows  TTL  of  the probe, followed by colon.  Usually value of TTL is
       obtained from reply from network, but sometimes reply does not contain necessary  informa-
       tion and we have to guess it. In this case the number is followed by ?.

       The second column shows the network hop, which replied to the probe.  It is either address
       of router or word [LOCALHOST], if the probe was not sent to the network.

       The rest of line shows miscellaneous information about path to the  correspinding  hetwork
       hop.  As  rule  it  contains  value  of	RTT.  Additionally, it can show Path MTU, when it
       changes.  If the path is asymmetric or the probe finishes before it reach prescribed  hop,
       difference between number of hops in forward and backward direction is shown folloing key-
       word async. This information is not reliable.  F.e. the third line shows asymmetry  of  1,
       it  is because the first probe with TTL of 2 was rejected at the first hop due to Path MTU
       Discovery.

       Te last line summarizes information about all  the  path  to  the  destination,	it  shows
       detected  Path  MTU,  amount of hops to the destination and our guess about amount of hops
       from the destination to us, which can be different when the path is asymmetric.

SEE ALSO
       traceroute(8), traceroute6(8), ping(8).

AUTHOR
       tracepath was written by Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>.

SECURITY
       No security issues.

       This lapidary deserves to be elaborated.  tracepath is not a  privileged  program,  unlike
       traceroute, ping and other beasts of this kind.	tracepath may be executed by everyone who
       has some access to network, enough to send UDP datagrams to investigated destination using
       given port.

AVAILABILITY
       tracepath is part of iputils package and the latest versions are  available in source form
       from anonymous ftp ftp://ftp.inr.ac.ru/ip-routing/iputils-current.tar.gz.

iputils-020927				27 September 2002			     TRACEPATH(8)


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