traceroute原理

traceroute原理

ICMP

ICMP全称为Internet Control Message Protocol，即，网络控制报文协议。

当一个IP数据报发送失败时，最后一个路由器会向发送发传递一条ICMP报文以报告错误。

traceroute利用此特性来探测路由。

原理如下，构造一份非法的数据，通过IP协议发送。第一份报文设置TTL为1，这样，第一个路由收到之后，就会给发送主机报告一个错误，这样，发送主机就知道此路由的第一跳。接着，设置TTL为2再次发送，第二个路由器也会报告错误。以此类推。

traceroute在windows上的名称为tracert。

C:\Users\Administrator>tracert www.baidu.com

通过最多 30 个跃点跟踪
到 www.a.shifen.com [180.97.33.108] 的路由:

1     1 ms     1 ms     1 ms  192.168.1.1
2    14 ms    22 ms    13 ms  100.64.0.1
3     5 ms     6 ms     8 ms  218.2.131.217
4     5 ms     7 ms     6 ms  202.102.69.26
5     *        *        *     请求超时。
6    10 ms     6 ms     5 ms  180.97.32.86
7     5 ms     5 ms     3 ms  10.203.195.2
8     6 ms     3 ms     3 ms  180.97.33.108

*:first-child {
margin-top: 0 !important;
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body>*:last-child {
margin-bottom: 0 !important;
}

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=============================================================================*/

p, blockquote, ul, ol, dl, table, pre {
margin: 15px 0;
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=============================================================================*/

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padding: 0;
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h6 {
color: #777;
font-size: 14px;
}

body>h2:first-child, body>h1:first-child, body>h1:first-child+h2, body>h3:first-child, body>h4:first-child, body>h5:first-child, body>h6:first-child {
margin-top: 0;
padding-top: 0;
}

a:first-child h1, a:first-child h2, a:first-child h3, a:first-child h4, a:first-child h5, a:first-child h6 {
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h1+p, h2+p, h3+p, h4+p, h5+p, h6+p {
margin-top: 10px;
}

/* LINKS
=============================================================================*/

a {
color: #4183C4;
text-decoration: none;
}

a:hover {
text-decoration: underline;
}

/* LISTS
=============================================================================*/

ul, ol {
padding-left: 30px;
}

ul li > :first-child,
ol li > :first-child,
ul li ul:first-of-type,
ol li ol:first-of-type,
ul li ol:first-of-type,
ol li ul:first-of-type {
margin-top: 0px;
}

ul ul, ul ol, ol ol, ol ul {
margin-bottom: 0;
}

dl {
padding: 0;
}

dl dt {
font-size: 14px;
font-weight: bold;
font-style: italic;
padding: 0;
margin: 15px 0 5px;
}

dl dt:first-child {
padding: 0;
}

dl dt>:first-child {
margin-top: 0px;
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dl dt>:last-child {
margin-bottom: 0px;
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dl dd {
margin: 0 0 15px;
padding: 0 15px;
}

dl dd>:first-child {
margin-top: 0px;
}

dl dd>:last-child {
margin-bottom: 0px;
}

/* CODE
=============================================================================*/

pre, code, tt {
font-size: 12px;
font-family: Consolas, "Liberation Mono", Courier, monospace;
}

code, tt {
margin: 0 0px;
padding: 0px 0px;
white-space: nowrap;
border: 1px solid #eaeaea;
background-color: #f8f8f8;
border-radius: 3px;
}

pre>code {
margin: 0;
padding: 0;
white-space: pre;
border: none;
background: transparent;
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pre {
background-color: #f8f8f8;
border: 1px solid #ccc;
font-size: 13px;
line-height: 19px;
overflow: auto;
padding: 6px 10px;
border-radius: 3px;
}

pre code, pre tt {
background-color: transparent;
border: none;
}

kbd {
-moz-border-bottom-colors: none;
-moz-border-left-colors: none;
-moz-border-right-colors: none;
-moz-border-top-colors: none;
background-color: #DDDDDD;
background-image: linear-gradient(#F1F1F1, #DDDDDD);
background-repeat: repeat-x;
border-color: #DDDDDD #CCCCCC #CCCCCC #DDDDDD;
border-image: none;
border-radius: 2px 2px 2px 2px;
border-style: solid;
border-width: 1px;
font-family: "Helvetica Neue",Helvetica,Arial,sans-serif;
line-height: 10px;
padding: 1px 4px;
}

/* QUOTES
=============================================================================*/

blockquote {
border-left: 4px solid #DDD;
padding: 0 15px;
color: #777;
}

blockquote>:first-child {
margin-top: 0px;
}

blockquote>:last-child {
margin-bottom: 0px;
}

/* HORIZONTAL RULES
=============================================================================*/

hr {
clear: both;
margin: 15px 0;
height: 0px;
overflow: hidden;
border: none;
background: transparent;
border-bottom: 4px solid #ddd;
padding: 0;
}

/* TABLES
=============================================================================*/

table th {
font-weight: bold;
}

table th, table td {
border: 1px solid #ccc;
padding: 6px 13px;
}

table tr {
border-top: 1px solid #ccc;
background-color: #fff;
}

table tr:nth-child(2n) {
background-color: #f8f8f8;
}

/* IMAGES
=============================================================================*/

img {
max-width: 100%
}
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