TRACEPATH(8)                       iputils                      TRACEPATH(8)

NAME         top

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

SYNOPSIS         top

       tracepath [-4] [-6] [-n] [-b] [-l pktlen] [-m max_hops] [-p port]
                 [-V] {destination}

DESCRIPTION         top

       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 require superuser privileges and has no fancy options.

       tracepath -6 is 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 will be
       updated. For now it uses Van Jacobson's trick, sweeping a range of
       UDP ports to maintain trace history.

OPTIONS         top

           Use IPv4 only..

           Use IPv6 only..

           Print primarily IP addresses numerically.

           Print both of host names and IP addresses.

           Sets the initial packet length to pktlen instead of 65535 for
           IPv4 or 128000 for IPv6.

           Set maximum hops (or maximum TTLs) to max_hops instead of 30.

           Sets the initial destination port to use.

           Print version and exit.

OUTPUT         top

           root@mops:~ # tracepath -6 3ffe:2400:0:109::2
            1?: [LOCALHOST]                              pmtu 1500
            1:                   0.411ms
            2:        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 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
       corresponding network 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 following keyword 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

       The 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         top

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

AUTHOR         top

       tracepath was written by Alexey Kuznetsov <>.

SECURITY         top

       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         top

       tracepath is part of iputils package.

COLOPHON         top

       This page is part of the iputils (IP utilities) project.  Information
       about the project can be found at ⟨⟩.
       If you have a bug report for this manual page, send it to,  This page was obtained
       from the project's upstream Git repository
       ⟨⟩ on 2019-05-09.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2019-04-19.)  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

iputils s20190324                                               TRACEPATH(8)

Pages that refer to this page: ip(7)arping(8)clockdiff(8)