Re: What can I do to UNDERSTAND why I can't reach centos.org (but everyone else can)?

[Les Mikesell <lesmikesell@xxxxxxxxx>]

On Fri, Mar 1, 2013 at 10:47 AM, Rock <RockSockDoc@xxxxxxxxx> wrote:
>
>> Those 'looking glass' sites can show you if the bgp
>> routes are propagating to various locations.
>
> I saw the reference to the lookingglass site, e.g.,
>  http://www.lookinglass.org
> But, I'm sorry ... I'm totally clueless as to how to properly USE them.
>
> May I ask:
> Q: Which of the IP addresses below do I put into lookingglass to gather data?

If you thing the problem is on your side, try ping/traceroute to your
own IP from some other locations.

> Given that these all died as follows:
>  $ traceroute tempotv.com.tr ==> died on the 23rd hop
> 19  82.222.13.145 (82.222.13.145)  262.456 ms 82.222.3.117 (82.222.3.117)  270.129 ms  273.278 ms
> 20  82.222.13.106 (82.222.13.106)  276.814 ms  276.812 ms  276.797 ms
> 21  82.222.253.82 (82.222.253.82)  273.131 ms  264.450 ms  247.432 ms
> 22  82.222.254.210 (82.222.254.210)  247.354 ms  247.362 ms 82.222.224.234 (82.222.224.234)  309.858 ms
> 23  asy60.asy53.tellcom.com.tr (92.45.53.60)  326.022 ms  329.493 ms  329.483 ms
> 24  * * *  (and so on)

It is very common for organizations to block ICMP at their private
border routers and just let a few port/address combinations through
for the public services they provide, so not reaching a target does
not mean there is a problem.   Sometimes you can reach the target with
tcptracroute (or traceroute -T -p port), but some intermediate hops
may not show because their ICMP replies are blocked.

Organizations that are multi-homed and do their own BGP routing will
have fairly specific routes showing up in the bgp tables that you can
query from the looking glass tools and if they fall completely off the
grid the routes will disappear.

-- 
   Les Mikesell
     lesmikesell@xxxxxxxxx
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