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Asterisks keep going in traceroute

Unix & Linux Asked by Amirreza A. on November 6, 2021

I know that asterisks mean that the router didn’t send the ICMP message back saying that TTL was 0 and I had to dump the request.

but sometimes for some cases when I want to check for the path of my packets to a server, at some point it keeps printing * * * and never ends. Even when I set -h flag (or -m flag depending on your operating system) to 255 which is the maximum number of TTL, it keeps printing asterisks to the end, I mean clearly my packet doesn’t need to take 255 hops to the destination.

Here is an example for microsoft.com

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.

One Answer

This has been increasingly common over the past decade as more and more network administrators decide that black-holing ICMP traffic is a good idea (whether or not it is is out of scope of this answer). Because traceroute uses ICMP traffic, when it encounters a node which does not accept or respond to them, it appears in the report that the host doing so is timing out.

As a result, newer tools such as mtr have become available which do effectively the same thing that traceroute does, but using TCP packets rather than ICMP packets.

Answered by DopeGhoti on November 6, 2021

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