0 前言
网络信息是电脑网络信息安全检查中的一块重要内容，Linux和基于Linux的操作系统，提供了很多的网络命令，今天我们研究tracepath命令。
Tracepath 在大多数 Linux 发行版中都是可用的。如果在你的系统中没有预装，请根据你的发行版使用下面的命令进行安装。
Windows中没有tracepath命令。
1 tracepath命令 的功能、格式和选项说明
1.1 tracepath命令 的功能
tracepath命令的功能是追踪数据包的路由信息，它可以追踪并显示数据包到达目的主机所经过的路由信息，以及对应的MTU值。
tracepath 与 traceroute 类似，用于确定数据包访问目的地所经历的路由路径。
Tracepath 特别适用于没有 root 权限的用户，因为它不需要特权即可运行。
1.2 tracepath命令 的格式
跟ping命令一样，我们可以使用 tracepath 或 tracepath -?命令获取ping命令的格式信息。 tracepath不支持 --?选项。
[purpleendurer @ bash ~] tracepath
Usage: tracepath [-n] [-b] [-l <len>] [-p port] <destination>
[purpleendurer @ bash ~] tracepath -?
Usage: tracepath [-n] [-b] [-l <len>] [-p port] <destination>
[purpleendurer @ bash ~] tracepath --?
tracepath: invalid option -- '-'
Usage: tracepath [-n] [-b] [-l <len>] [-p port] <destination>
[purpleendurer @ bash ~] 
tracepath [-n] [-b] [-l <最大路径长度>] [-p 端口号] <目标域名或IP地址>
1.3 tracepath命令选项说明
与ping命令相比，tracepath的命令不算多。
不过不同版本的Linux提供的tracepath命令选项不尽相同。
| 选项 | 说明 |
|---|---|
| -n | 输出数字格式的地址 |
| -b | 输出回程路径 |
| -l 最大路径长度 | 设置最大路径长度 |
| -m 最大TTL值 | 设置查询的最大TTL值 |
| -p 端口号 | 设置UDP端口号 |
| -V | 显示版本信息 |
2 tracepath命令实例
2.1 tracepath g.cn
[purpleendurer @ bash ~] tracepath g.cn1?: [LOCALHOST] pmtu 15001: 26.10.178.42 2.037ms 1: 26.10.178.42 2.238ms 2: 11.73.57.238 1.986ms 3: 11.73.37.65 1.852ms 4: 11.73.49.81 3.004ms 5: 10.222.215.161 2.377ms 6: 10.54.171.129 3.831ms 7: 10.102.154.246 4.610ms asymm 6 8: no reply9: no reply
10: 61.149.190.38 5.299ms asymm 9
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[purpleendurer @ bash ~] 
命令返回信息中的PMTU （Path Maximum Transmission Unit，数据通信网络中发现路径最大传输单元）是优化网络性能的关键技术之一。PMTU决定了数据在网络中传输的最大数据包大小 。
2.2 tracepath -b g.cn ：输出回程路径
[purpleendurer @ bash ~] tracepath -b g.cn1?: [LOCALHOST] pmtu 15001: 26.10.178.42 (26.10.178.42) 2.308ms 2: 11.73.56.206 (11.73.56.206) 1.952ms 3: 11.73.31.193 (11.73.31.193) 2.034ms 4: 11.73.48.73 (11.73.48.73) 2.678ms 5: 10.222.214.217 (10.222.214.217) 15.309ms 6: 10.54.171.141 (10.54.171.141) 3.707ms 7: 10.102.154.222 (10.102.154.222) 4.003ms 8: no reply9: no reply
10: 114.243.132.194 (114.243.132.194) 5.394ms asymm 9
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[purpleendurer @ bash ~] 
2.3 tracepath -l 512 g.cn：设置最大路径长度为512
[purpleendurer @ bash ~] tracepath -l 512 g.cn1: 26.10.178.42 2.625ms 2: 11.73.56.206 1.956ms 3: 11.73.37.161 1.943ms 4: 11.73.50.209 3.318ms 5: 10.222.214.241 3.257ms 6: 11.94.197.101 3.779ms asymm 7 7: 116.251.112.161 4.019ms asymm 6 8: no reply9: no reply
10: 114.243.132.194 5.299ms asymm 9
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[purpleendurer @ bash ~] 
2.4 tracepath -p 80 g.cn：使用UDP 80端口
[purpleendurer @ bash ~] tracepath -p 80 g.cn1?: [LOCALHOST] pmtu 15001: 26.10.178.42 2.337ms 1: 26.10.178.42 2.357ms 2: 11.73.56.78 1.909ms 3: 11.73.36.129 1.877ms 4: 11.73.43.185 2.385ms 5: 10.222.214.193 2.221ms 6: 10.54.171.221 3.892ms 7: 116.251.112.157 3.971ms asymm 6 8: no reply9: 125.33.184.177 4.492ms asymm 8
10: 114.243.132.194 4.819ms asymm 9
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[purpleendurer @ bash ~] 
2.5 tracepath -n g.cn ：输出数字格式的地址
[purpleendurer @ bash ~] tracepath -n g.cn1?: [LOCALHOST] pmtu 15001: 26.10.178.42 2.073ms 1: 26.10.178.42 2.068ms 2: 11.73.57.174 1.826ms 3: 11.73.32.57 2.603ms 4: 11.73.52.81 2.285ms 5: 10.222.215.113 2.359ms 6: 10.54.171.141 3.860ms 7: 10.102.154.234 3.791ms 8: no reply9: no reply
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30: no replyToo many hops: pmtu 1500Resume: pmtu 1500
[purpleendurer @ bash ~] 
