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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OUTPUT | SEE ALSO | AUTHOR | SECURITY | AVAILABILITY | COLOPHON |
TRACEPATH(8) iputils TRACEPATH(8)
tracepath - traces path to a network host discovering MTU along this
path
tracepath [-4] [-6] [-n] [-b] [-l pktlen] [-m max_hops] [-p port]
[-V] {destination}
It traces the network path to destination discovering MTU along this
path. It uses UDP port port or some random port. It is similar to
traceroute. However, it does not require superuser privileges and has
no fancy options.
tracepath -6 is a good replacement for traceroute6 and classic
example of application of Linux error queues. The situation with IPv4
is worse, because commercial IP routers do not return enough
information in ICMP error messages. Probably, it will change, when
they are updated. For now it uses Van Jacobson's trick, sweeping a
range of UDP ports to maintain trace history.
-4
Use IPv4 only.
-6
Use IPv6 only.
-n
Print primarily IP addresses numerically.
-b
Print both: Host names and IP addresses.
-l
Sets the initial packet length to pktlen instead of 65535 for
IPv4 or 128000 for IPv6.
-m
Set maximum hops (or maximum TTLs) to max_hops instead of 30.
-p
Sets the initial destination port to use.
-V
Print version and exit.
root@mops:~ # tracepath -6 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 the TTL of the probe, followed by colon.
Usually the value of TTL is obtained from the reply from the network,
but sometimes it does not contain the necessary information 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 the address of the router or the word [LOCALHOST], if
the probe was not sent to the network.
The rest of the line shows miscellaneous information about the path
to the corresponding network hop. It contains the value of RTT, and
additionally it can show Path MTU when it changes. If the path is
asymmetric or the probe finishes before it reaches the prescribed
hop, the difference between number of hops in forward and return
direction is shown next to the keyword "async". This information is
not reliable, e.g. the third line shows asymmetry of 1. This is
because the first probe with TTL of 2 was rejected at the first hop
due to Path MTU Discovery.
The last line summarizes information about all the paths to the
destination. It shows detected Path MTU, amount of hops to the
destination and our guess about the number of hops from the
destination to us, which can be different when the path is
asymmetric.
traceroute(8), traceroute6(8), ping(8).
tracepath was written by Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>.
No security issues.
This lapidary deserves to be elaborated. tracepath is not a
privileged program, unlike traceroute, ping and other beasts of their
kind. tracepath may be executed by everyone who has enough access to
the network to send UDP datagrams to the desired destination using
the given port.
tracepath is part of iputils package.
This page is part of the iputils (IP utilities) project. Information
about the project can be found at ⟨http://www.skbuff.net/iputils/⟩.
If you have a bug report for this manual page, send it to
yoshfuji@skbuff.net, netdev@vger.kernel.org. This page was obtained
from the project's upstream Git repository
⟨https://github.com/iputils/iputils.git⟩ on 2020-08-13. (At that
time, the date of the most recent commit that was found in the repos‐
itory was 2020-08-10.) If you discover any rendering problems in
this HTML version of the page, or you believe there is a better or
more up-to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not part
of the original manual page), send a mail to man-pages@man7.org
iputils s20190709 TRACEPATH(8)
Pages that refer to this page: ip(7) , arping(8) , clockdiff(8)