What can I do to UNDERSTAND why, periodically, I can't reach www.centos.org (but everyone else can)?
Every few months, http://www.centos.org just drops off for me and for me only. It's not the web site, because I can reach it via a proxy (e.g., TOR browser bundle) and other tests show it to be alive (e.g., http://www.downforeveryoneorjustme.com/centos.org or http://traceroute.monitis.com).
But, for me, I just can't reach it by any means.
Mike Easter kindly determined "centos.org does not echo ICMP or UDP pings, only TCP, and its associated netblock level3 doesn't echo UDP, but does echo ICMP and TCP."
But, for me, this is what a traceroute returned just now on Centos:
$ traceroute www.centos.org ... early hops removed ... 16 ae-6-6.ebr2.LosAngeles1.Level3.net (4.69.148.201) 211.850 ms ae-3-3.ebr3.Dallas1.Level3.net (4.69.132.78) 205.221 ms ae-6-6.ebr2.LosAngeles1.Level3.net (4.69.148.201) 207.392 ms 17 ae-3-3.ebr3.Dallas1.Level3.net (4.69.132.78) 128.453 ms ae-73-73.csw2.Dallas1.Level3.net (4.69.151.145) 160.451 ms ae-93-93.csw4.Dallas1.Level3.net (4.69.151.169) 160.437 ms 18 ae-83-83.csw3.Dallas1.Level3.net (4.69.151.157) 165.923 ms ae-1-60.edge3.Dallas1.Level3.net (4.69.145.8) 165.920 ms 178.414 ms 19 LAYERED-TEC.edge3.Dallas1.Level3.net (4.71.170.6) 241.537 ms 244.324 ms ae-3-80.edge3.Dallas1.Level3.net (4.69.145.136) 244.318 ms 20 * LAYERED-TEC.edge3.Dallas1.Level3.net (4.71.170.6) 244.291 ms 244.250 ms 21 * * * 22 * * * 23 * * * 24 * * * 25 * * * 26 * * * 27 * * * 28 * * * 29 * * * 30 * * *
Here is a screenshot (modified to remove early hops) using mtr: $ mtr www.centos.org http://www2.picturepush.com/photo/a/12303130/img/12303130.png
My related questions are: 1. What can I do (on Centos) to UNDERSTAND this problem? 2. Why does this problem happen every few months to me (and to just me)? 3. How can the net be this arbitrary and still work?