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MAN page from Trustix iputils-0.0.20020927-8tr.i586.rpm

TRACEPATH

Section: System Manager's Manual: iputils (8)
Updated: 27 September 2002
Index 

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 superuserprivileges and has no fancy options.

tracepath6 is good replacement for traceroute6and classic example of application of Linux error queues.The situation with tracepath is worse, because commercialIP 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 rangeof UDP ports to maintain trace history. 

OUTPUT

rootAATTmops:~ # 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 information andwe 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], ifthe probe was not sent to the network.

The rest of line shows miscellaneous information about path tothe correspinding hetwork hop. As rule it contains value of RTT.Additionally, it can show Path MTU, when it changes.If the path is asymmetricor the probe finishes before it reach prescribed hop, differencebetween number of hops in forward and backward direction is shownfolloing keyword async. This information is not reliable.F.e. the third line shows asymmetry of 1, it is because the first probewith 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 ourguess about amount of hops from the destination to us, which can bedifferent when the path is asymmetric. 

SEE ALSO

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

AUTHOR

tracepath was written byAlexey Kuznetsov<kuznetAATTms2.inr.ac.ru>. 

SECURITY

No security issues.

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

AVAILABILITY

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


 

Index

NAME
SYNOPSIS
DESCRIPTION
OUTPUT
SEE ALSO
AUTHOR
SECURITY
AVAILABILITY

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