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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. |