Rock wrote:
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.
Could you define "me"? Are you using this at home, or at work? What kind of connection? If this is work, are you paying for a fix IP?
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
Interesting. I get to 20 (except for me it's 15), and www.centos.org is the next hop (16). Now, I *do* have fat pipes and good connections (this is a US fed gov't site), but still.... <snip>
My related questions are:
- What can I do (on Centos) to UNDERSTAND this problem?
- Why does this problem happen every few months to me (and to just me)?
- How can the net be this arbitrary and still work?
Have you spoken to your ISP? When you try the traceroute, and it fails, have you tried other well-known locations, like google.com, or slashdot.org?
Also, have you compared the contents of /etc/resolv.conf now, and again when centos.org isn't visible?
Sounds like either a firewall, spam, or nameserver issue.
mark