| 1 | .\" This manpage has been automatically generated by docbook2man |
| 2 | .\" from a DocBook document. This tool can be found at: |
| 3 | .\" <http://shell.ipoline.com/~elmert/comp/docbook2X/> |
| 4 | .\" Please send any bug reports, improvements, comments, patches, |
| 5 | .\" etc. to Steve Cheng <steve@ggi-project.org>. |
| 6 | .TH "TRACEPATH" "8" "07 May 2014" "iputils-121221" "System Manager's Manual: iputils" |
| 7 | .SH NAME |
| 8 | tracepath, tracepath6 \- traces path to a network host discovering MTU along this path |
| 9 | .SH SYNOPSIS |
| 10 | |
| 11 | \fBtracepath\fR [\fB-n\fR] [\fB-b\fR] [\fB-l \fIpktlen\fB\fR] [\fB-m \fImax_hops\fB\fR] [\fB-p \fIport\fB\fR] \fB\fIdestination\fB\fR |
| 12 | |
| 13 | .SH "DESCRIPTION" |
| 14 | .PP |
| 15 | It traces path to \fIdestination\fR discovering MTU along this path. |
| 16 | It uses UDP port \fIport\fR or some random port. |
| 17 | It is similar to \fBtraceroute\fR, only does not require superuser |
| 18 | privileges and has no fancy options. |
| 19 | .PP |
| 20 | \fBtracepath6\fR is good replacement for \fBtraceroute6\fR |
| 21 | and classic example of application of Linux error queues. |
| 22 | The situation with IPv4 is worse, because commercial |
| 23 | IP routers do not return enough information in ICMP error messages. |
| 24 | Probably, it will change, when they will be updated. |
| 25 | For now it uses Van Jacobson's trick, sweeping a range |
| 26 | of UDP ports to maintain trace history. |
| 27 | .SH "OPTIONS" |
| 28 | .TP |
| 29 | \fB-n\fR |
| 30 | Print primarily IP addresses numerically. |
| 31 | .TP |
| 32 | \fB-b\fR |
| 33 | Print both of host names and IP addresses. |
| 34 | .TP |
| 35 | \fB-l\fR |
| 36 | Sets the initial packet length to \fIpktlen\fR instead of |
| 37 | 65535 for \fBtracepath\fR or 128000 for \fBtracepath6\fR. |
| 38 | .TP |
| 39 | \fB-m/term> \fR |
| 40 | Set maximum hops (or maximum TTLs) to \fImax_hops\fR |
| 41 | instead of 30. |
| 42 | .TP |
| 43 | \fB-p\fR |
| 44 | Sets the initial destination port to use. |
| 45 | .SH "OUTPUT" |
| 46 | .PP |
| 47 | |
| 48 | .nf |
| 49 | root@mops:~ # tracepath6 3ffe:2400:0:109::2 |
| 50 | 1?: [LOCALHOST] pmtu 1500 |
| 51 | 1: dust.inr.ac.ru 0.411ms |
| 52 | 2: dust.inr.ac.ru asymm 1 0.390ms pmtu 1480 |
| 53 | 2: 3ffe:2400:0:109::2 463.514ms reached |
| 54 | Resume: pmtu 1480 hops 2 back 2 |
| 55 | .fi |
| 56 | .PP |
| 57 | The first column shows TTL of the probe, followed by colon. |
| 58 | Usually value of TTL is obtained from reply from network, |
| 59 | but sometimes reply does not contain necessary information and |
| 60 | we have to guess it. In this case the number is followed by ?. |
| 61 | .PP |
| 62 | The second column shows the network hop, which replied to the probe. |
| 63 | It is either address of router or word [LOCALHOST], if |
| 64 | the probe was not sent to the network. |
| 65 | .PP |
| 66 | The rest of line shows miscellaneous information about path to |
| 67 | the correspinding network hop. As rule it contains value of RTT. |
| 68 | Additionally, it can show Path MTU, when it changes. |
| 69 | If the path is asymmetric |
| 70 | or the probe finishes before it reach prescribed hop, difference |
| 71 | between number of hops in forward and backward direction is shown |
| 72 | following keyword async. This information is not reliable. |
| 73 | F.e. the third line shows asymmetry of 1, it is because the first probe |
| 74 | with TTL of 2 was rejected at the first hop due to Path MTU Discovery. |
| 75 | .PP |
| 76 | The last line summarizes information about all the path to the destination, |
| 77 | it shows detected Path MTU, amount of hops to the destination and our |
| 78 | guess about amount of hops from the destination to us, which can be |
| 79 | different when the path is asymmetric. |
| 80 | .SH "SEE ALSO" |
| 81 | .PP |
| 82 | \fBtraceroute\fR(8), |
| 83 | \fBtraceroute6\fR(8), |
| 84 | \fBping\fR(8). |
| 85 | .SH "AUTHOR" |
| 86 | .PP |
| 87 | \fBtracepath\fR was written by |
| 88 | Alexey Kuznetsov |
| 89 | <kuznet@ms2.inr.ac.ru>. |
| 90 | .SH "SECURITY" |
| 91 | .PP |
| 92 | No security issues. |
| 93 | .PP |
| 94 | This lapidary deserves to be elaborated. |
| 95 | \fBtracepath\fR is not a privileged program, unlike |
| 96 | \fBtraceroute\fR, \fBping\fR and other beasts of this kind. |
| 97 | \fBtracepath\fR may be executed by everyone who has some access |
| 98 | to network, enough to send UDP datagrams to investigated destination |
| 99 | using given port. |
| 100 | .SH "AVAILABILITY" |
| 101 | .PP |
| 102 | \fBtracepath\fR is part of \fIiputils\fR package |
| 103 | and the latest versions are available in source form at |
| 104 | http://www.skbuff.net/iputils/iputils-current.tar.bz2. |