{ "mode": "man", "parameter": "tracepath", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/tracepath/8/json", "generated": "2026-06-02T21:27:07Z", "synopsis": "tracepath [-4] [-6] [-n] [-b] [-l pktlen] [-m maxhops] [-p port] [-V] {destination}", "sections": { "NAME": { "content": "tracepath - traces path to a network host discovering MTU along this path\n", "subsections": [] }, "SYNOPSIS": { "content": "tracepath [-4] [-6] [-n] [-b] [-l pktlen] [-m maxhops] [-p port] [-V] {destination}\n", "subsections": [] }, "DESCRIPTION": { "content": "It traces the network path to destination discovering MTU along this path. It uses UDP port\nport or some random port. It is similar to traceroute. However, it does not require superuser\nprivileges and has no fancy options.\n\ntracepath -6 is a good replacement for traceroute6 and classic example of application of\nLinux error queues. The situation with IPv4 is worse, because commercial IP routers do not\nreturn enough information in ICMP error messages. Probably, it will change, when they are\nupdated. For now it uses Van Jacobson's trick, sweeping a range of UDP ports to maintain\ntrace history.\n", "subsections": [] }, "OPTIONS": { "content": "", "subsections": [ { "name": "-4", "content": "Use IPv4 only.\n", "flag": "-4" }, { "name": "-6", "content": "Use IPv6 only.\n", "flag": "-6" }, { "name": "-n", "content": "Print primarily IP addresses numerically.\n", "flag": "-n" }, { "name": "-b", "content": "Print both: Host names and IP addresses.\n", "flag": "-b" }, { "name": "-l", "content": "Sets the initial packet length to pktlen instead of 65535 for IPv4 or 128000 for IPv6.\n", "flag": "-l" }, { "name": "-m", "content": "Set maximum hops (or maximum TTLs) to maxhops instead of 30.\n", "flag": "-m" }, { "name": "-p", "content": "Sets the initial destination port to use.\n", "flag": "-p" }, { "name": "-V", "content": "Print version and exit.\n", "flag": "-V" } ] }, "OUTPUT": { "content": "root@mops:~ # tracepath -6 3ffe:2400:0:109::2\n1?: [LOCALHOST] pmtu 1500\n1: dust.inr.ac.ru 0.411ms\n2: dust.inr.ac.ru asymm 1 0.390ms pmtu 1480\n2: 3ffe:2400:0:109::2 463.514ms reached\nResume: pmtu 1480 hops 2 back 2\n\n\nThe first column shows the TTL of the probe, followed by colon. Usually the value of TTL is\nobtained from the reply from the network, but sometimes it does not contain the necessary\ninformation and we have to guess it. In this case the number is followed by ?.\n\nThe second column shows the network hop which replied to the probe. It is either the address\nof the router or the word [LOCALHOST], if the probe was not sent to the network.\n\nThe rest of the line shows miscellaneous information about the path to the corresponding\nnetwork hop. It contains the value of RTT, and additionally it can show Path MTU when it\nchanges. If the path is asymmetric or the probe finishes before it reaches the prescribed\nhop, the difference between number of hops in forward and return direction is shown next to\nthe keyword \"async\". This information is not reliable, e.g. the third line shows asymmetry of\n1. This is because the first probe with TTL of 2 was rejected at the first hop due to Path\nMTU Discovery.\n\nThe last line summarizes information about all the paths to the destination. It shows\ndetected Path MTU, amount of hops to the destination and our guess about the number of hops\nfrom the destination to us, which can be different when the path is asymmetric.\n", "subsections": [] }, "SEE ALSO": { "content": "traceroute(8), traceroute6(8), ping(8).\n", "subsections": [] }, "AUTHOR": { "content": "tracepath was written by Alexey Kuznetsov .\n", "subsections": [] }, "SECURITY": { "content": "No security issues.\n\nThis lapidary deserves to be elaborated. tracepath is not a privileged program, unlike\ntraceroute, ping and other beasts of their kind. tracepath may be executed by everyone who\nhas enough access to the network to send UDP datagrams to the desired destination using the\ngiven port.\n", "subsections": [] }, "AVAILABILITY": { "content": "tracepath is part of iputils package.\n\n\n\niputils 20211215 TRACEPATH(8)", "subsections": [] } }, "summary": "tracepath - traces path to a network host discovering MTU along this path", "flags": [ { "flag": "-4", "long": null, "arg": null, "description": "Use IPv4 only." }, { "flag": "-6", "long": null, "arg": null, "description": "Use IPv6 only." }, { "flag": "-n", "long": null, "arg": null, "description": "Print primarily IP addresses numerically." }, { "flag": "-b", "long": null, "arg": null, "description": "Print both: Host names and IP addresses." }, { "flag": "-l", "long": null, "arg": null, "description": "Sets the initial packet length to pktlen instead of 65535 for IPv4 or 128000 for IPv6." }, { "flag": "-m", "long": null, "arg": null, "description": "Set maximum hops (or maximum TTLs) to maxhops instead of 30." }, { "flag": "-p", "long": null, "arg": null, "description": "Sets the initial destination port to use." }, { "flag": "-V", "long": null, "arg": null, "description": "Print version and exit." } ], "examples": [], "see_also": [ { "name": "traceroute", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/traceroute/8/json" }, { "name": "traceroute6", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/traceroute6/8/json" }, { "name": "ping", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/ping/8/json" } ], "tldr": { "source": "official", "description": "Trace the path to a network host discovering MTU along this path.", "examples": [ { "description": "A preferred way to trace the path to a host", "command": "tracepath -p {{33434}} {{host}}" }, { "description": "Specify the initial destination port, useful with non-standard firewall settings", "command": "tracepath -p {{destination_port}} {{host}}" }, { "description": "Print both hostnames and numerical IP addresses", "command": "tracepath -b {{host}}" }, { "description": "Specify a maximum TTL (number of hops)", "command": "tracepath -m {{max_hops}} {{host}}" }, { "description": "Specify the initial packet length (defaults to 65535 for IPv4 and 128000 for IPv6)", "command": "tracepath -l {{packet_length}} {{host}}" }, { "description": "Use only IPv6 addresses", "command": "tracepath -6 {{host}}" } ] } }