[CentOS] What can I do to UNDERSTAND why I can't reach centos.org (but everyone else can)?

[m.roth at 5-cent.us]

Rock wrote:
> On Thu, 28 Feb 2013 13:40:55 -0500, m.roth-x6lchVBUigD1P9xLtpHBDw wrote:
>
>> 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 fixed IP?
>
> I have a fixed IP address at home.
>
>> I get to 20 (except for me it's 15), and www.centos.org is
>> the next hop (16).
>
> After hashing this out on alt.comp.freeware all morning,
> someone surmised that my static public IP address might
> have been added to a blocklist in the past few days,
> either by the penultimate hop or by centos.org itself.
>
Oh. great. Have any bouncing mail when centos.org disappears? I have this
happen a number of times a year, and yell about it every time. They use
dnsorbs, who I say use a blacklisting methodology that worked 15 years
ago, but is a complete disaster now, when one hosting co (as I have now),
or ISP (say, roadrunner in Chicago, which provides one third or one half
of *all* of Chicago's net access), and both have mail go through one
mailserver address... and when a few idiots get their systems or sites
compromised, dnsorbs instead of blocking each domain, blocs ALL the
hundreds of thousands of folks innocently emailing through their service
provider or hosting site. They don't seem to parse headers, and go *past*
the mailserver to the culprit. Thank you, I prefer fail2ban's methodology.

> So, the question morphs to whether or not we have tools at
> our disposal which can pinpoint which entity is blocking my
> IP address?
>
> Note: I left a phone message at the DNS registrant for
> the penultimate hop and I left an email for the centos.org
> webmaster.
>
>> have you compared the contents of /etc/resolv.conf now,
>> and again when centos.org isn't visible?
>
> Well, I must admit I never even knew that file existed.
> Here is what it has in it:
>
> $ cat /etc/resolv.conf
>   # Generated by NetworkManager
>   nameserver 192.168.1.1
>
Right, that's given you by your cable modem or router. Can you see what
that is on that ISP-provided box? Alternatively, add well-known
nameservers to that file, which will be overwritten when it's working
again. For example, you could add
nameserver 8.8.8.8
nameserver 8.8.4.4
(see <https://developers.google.com/speed/public-dns/docs/using>)

   mark