Re: [OT] traceroute vigor help

[Kim Wall <kim@xxxxxxxxxxxxxxxxxx>]

aashram wrote:
> Can anyone help out with this one.
>
> I am trying to connect to a particular ip, but this one ip will not
> connect.
> I did a trace route but for some reason it does not get the
desination.
> I know the website works no problem as I have got others to try.

A couple of weeks ago, I ended up chasing up a similar issue for a
friend who was having trouble with their hosting service, here's a
potted summary:

Friend of mine admins http://www.ttales.net/, and was getting
reports of
various users having trouble seeing the site due to DNS problems.

With help from me, we resolve the DNS issue (the zonefile was a
recursive mess, probably eaten by the host's web front-end), and wait 24
hours for the changes to propagate.

Everyone who originally complained could now see the site.  But I
couldn't.  DNS was working fine, but my connection to the webserver was
timing out.  I could see the rest of the internet fine.

By chance, I discovered that it was just the machine my squid proxy was
running on that couldn't reach the site (I have a block of real IP
addresses from Nildram, and the other machines on my network could reach
the site fine).

ICMP traceroute from the proxy box showed the connection getting as far
as hosting company's ISP's router, then dying.

Changing MTU had no effect (path MTU discovery problems (see
http://www.netheaven.com/pmtu.html)
seemed like a likely cause).

After serious amounts of mucking about with tcpdump (which showed
absolutely no response from the server when connected to by anything
running on my proxy box), I eliminate OS related issues by swapping the
IP address with one of my windows boxes.  The problem was definitely IP
specific.

Am about to write carefully-crafted email to hosting company saying
"wtf?", when suddenly it starts working.  Presumably they changed
something at their end.


So yeah - these things can happen.  Try lowering your MTU to see if that
helps (If so, it's a misconfiguration at the other end).  Try
eliminating as much hardware/software at your end as you can.  If none
of that helps, email the ISPs involved, it could well be that your
address has found its way into some sort of blacklist.


kim.