# tracepath(8) - man - phpman

> **TLDR:** Trace the path to a network host discovering MTU along this path.
>
- A preferred way to trace the path to a host:
  `tracepath -p {{33434}} {{host}}`
- Specify the initial destination port, useful with non-standard firewall settings:
  `tracepath -p {{destination_port}} {{host}}`
- Print both hostnames and numerical IP addresses:
  `tracepath -b {{host}}`
- Specify a maximum TTL (number of hops):
  `tracepath -m {{max_hops}} {{host}}`
- Specify the initial packet length (defaults to 65535 for IPv4 and 128000 for IPv6):
  `tracepath -l {{packet_length}} {{host}}`
- Use only IPv6 addresses:
  `tracepath -6 {{host}}`

*Source: tldr-pages*

---

[TRACEPATH(8)](https://www.chedong.com/phpMan.php/man/TRACEPATH/8/markdown)                                   iputils                                  [TRACEPATH(8)](https://www.chedong.com/phpMan.php/man/TRACEPATH/8/markdown)



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

## SYNOPSIS
       **tracepath** [**-4**] [**-6**] [**-n**] [**-b**] [**-l** _pktlen_] [**-m** _max_hops_] [**-p** _port_] [**-V**] {destination}

## DESCRIPTION
       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.

## OPTIONS
### -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.

## OUTPUT
           root@mops:~ # tracepath -6 3ffe:2400:0:[109::2](https://www.chedong.com/phpMan.php/perldoc/109%3A%3A2/markdown)
            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](https://www.chedong.com/phpMan.php/perldoc/109%3A%3A2/markdown)               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.

## SEE ALSO
       [**traceroute**(8)](https://www.chedong.com/phpMan.php/man/traceroute/8/markdown), [**traceroute6**(8)](https://www.chedong.com/phpMan.php/man/traceroute6/8/markdown), [**ping**(8)](https://www.chedong.com/phpMan.php/man/ping/8/markdown).

## 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 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.

## AVAILABILITY
       **tracepath** is part of _iputils_ package.



iputils 20211215                                                                        [TRACEPATH(8)](https://www.chedong.com/phpMan.php/man/TRACEPATH/8/markdown)