我知道星号意味着路由器没有发回 ICMP 消息，说明 TTL 为 0，我必须转储请求。
但有时在某些情况下，当我想检查数据包到服务器的路径时，在某些时候它会不断打印 * * * 并且永远不会结束。即使当我将 -h 标志（或 -m 标志，具体取决于您的操作系统）设置为 255（TTL 的最大数量）时，它仍然会在末尾打印星号，我的意思显然是我的数据包不需要经过 255 跳才能到达目的地。
这是 microsoft.com 的示例
tracert -h 255 microsoft.com
Tracing route to microsoft.com [40.76.4.15]
over a maximum of 255 hops:
1 125 ms 127 ms 144 ms 10.10.10.232
2 148 ms 151 ms 125 ms 149.202.66.253
3 122 ms 129 ms 123 ms 10.50.60.61
4 139 ms 128 ms 127 ms 10.17.130.102
5 123 ms 125 ms 125 ms 10.73.0.6
6 150 ms 132 ms 134 ms 10.95.33.10
7 135 ms 131 ms 133 ms be100-1112.ams-5-a9.nl.eu [213.251.128.67]
8 160 ms 181 ms 181 ms ams-ix-2.microsoft.com [80.249.209.21]
9 169 ms 187 ms 131 ms ae25-0.icr02.ams21.ntwk.msn.net [104.44.239.77]
10 210 ms 210 ms 208 ms be-122-0.ibr02.ams21.ntwk.msn.net [104.44.22.245]
11 224 ms 218 ms 205 ms be-11-0.ibr02.lon24.ntwk.msn.net [104.44.16.2]
12 211 ms 208 ms 214 ms be-1-0.ibr02.lon22.ntwk.msn.net [104.44.16.57]
13 205 ms 211 ms 219 ms be-7-0.ibr02.nyc30.ntwk.msn.net [104.44.18.154]
14 211 ms 216 ms 211 ms 104.44.28.55
15 203 ms 224 ms 219 ms ae162-0.icr02.bl20.ntwk.msn.net [104.44.21.234]
16 * * * Request timed out.
17 * * * Request timed out.
18 * * * Request timed out.
19 * * * Request timed out.
20 * * * Request timed out.
21 * * * Request timed out.
22 * * * Request timed out.
23 * * * Request timed out.
24 * * * Request timed out.
25 * * * Request timed out.
26 * * * Request timed out.
27 * * * Request timed out.
28 * * * Request timed out.
29 * * * Request timed out.
30 * * * Request timed out.
31 * * * Request timed out.
32 * * * Request timed out.
33 * * * Request timed out.
34 * * * Request timed out.
35 * * * Request timed out.
36 * * * Request timed out.
37 * * * Request timed out.
38 * * * Request timed out.
39 * * * Request timed out.
40 * * * Request timed out.
41 * * * Request timed out.
42 * * * Request timed out.
43 * * * Request timed out.
44 * * * Request timed out.
45 * * * Request timed out.
46 * * * Request timed out.
47 * * * Request timed out.
48 * * * Request timed out.
49 * * * Request timed out.
50 * * * Request timed out.
51 * * * Request timed out.
52 * * * Request timed out.
53 * * * Request timed out.
54 * * * Request timed out.
55 * * * Request timed out.
56 * * * Request timed out.
57 * * * Request timed out.
58 * * * Request timed out.
59 * * * Request timed out.
60 * * * Request timed out.
61 * * * Request timed out.
62 * * * Request timed out.
63 * * * Request timed out.
64 * * * Request timed out.
65 * * * Request timed out.
66 * * * Request timed out.
67 * * * Request timed out.
68 * * * Request timed out.
69 * * * Request timed out.
70 * * * Request timed out.
71 * * * Request timed out.
72 * * * Request timed out.
73 * * * Request timed out.
74 * * * Request timed out.
75 * * * Request timed out.
76 * * * Request timed out.
77 * * * Request timed out.
78 * * * Request timed out.
79 * * * Request timed out.
80 * * * Request timed out.
81 * * * Request timed out.
答案1
在过去十年中，随着越来越多的网络管理员认为黑洞 ICMP 流量是一个好主意（无论是否超出了本答案的范围），这种情况变得越来越普遍。由于 Traceroute 使用 ICMP 流量，因此当它遇到不接受或不响应它们的节点时，报告中会显示这样做的主机超时。
因此，mtr出现了诸如此类的新工具，它们可以有效地完成与traceroute之前相同的操作，但使用 TCP 数据包而不是 ICMP 数据包。