tracepath的结果有点困惑

[pengsir]

tracepath forum.ubuntu.org.cn
1?: [LOCALHOST] pmtu 1500
1: 192.168.1.1 3.164ms
1: 192.168.1.1 12.867ms
2: 192.168.1.1 3.069ms pmtu 1492
2: 113.58.144.1 42.953ms
3: 221.11.165.9 44.810ms
4: 221.11.165.245 61.522ms asymm 7
5: 219.158.24.217 54.489ms asymm 6
6: 219.158.23.22 122.072ms
7: 219.158.97.30 169.597ms
8: 219.158.30.254 404.408ms
9: 199.102.95.5 317.132ms
10: 207.254.184.98 295.204ms
11: dist01.dc03.lax.ip4.scalabledns.com 270.719ms
12: dc03r04ds30.scalabledns.com 260.713ms
13: 192.157.242.155 274.252ms reached
Resume: pmtu 1492 hops 13 back 12

请看前几行
tracepath forum.ubuntu.org.cn
1?: [LOCALHOST] pmtu 1500
1: 192.168.1.1 3.164ms
1: 192.168.1.1 12.867ms
2: 192.168.1.1 3.069ms pmtu 1492
2: 113.58.144.1 42.953ms

为何 192.168.1.1 出现了3次，前面的标号 1 2 代表什么含义？
2: 192.168.1.1 3.069ms pmtu 1492
2: 113.58.144.1 42.953ms
为何这两行，前面的标号都是 2 ？

[poloshiao]

为何 192.168.1.1 出现了3次，前面的标号 1 2 代表什么含义？

1. http://manpages.ubuntu.com/manpages/kar ... ine.8.html
使用 hop 搜尋
hop 跳(一次)
預設最多 30 次

为何这两行，前面的标号都是 2 ？

2. http://manpages.ubuntu.com/manpages/wil ... ath.8.html
tracepath, tracepath6
沒有看到解釋

3. http://manpages.ubuntu.com/manpages/kar ... ine.8.html
traceroute
有類似的說明
3-1. EXAMPLES
2 lilac-dmc.Berkeley.EDU (128.32.216.1) 39 ms 39 ms 19 ms
3 lilac-dmc.Berkeley.EDU (128.32.216.1) 39 ms 39 ms 19 ms
Note that lines 2 & 3 are the same. This is due to a buggy kernel on the 2nd hop system -- lbl-csam.arpa -- that forwards packets with a zero TTL.