[Wylug-help] understanding traceroute output.

[Richard Wade]

On Mon, 10 Mar 2003, Simon Wood wrote:

> I have a problem with my internet connectivity. There are a (not insignif=
icant) number of websites that I can't access. This has been the case since=
 changing ISPs and their support department fails to find a solution claimi=
ng it is beyond their control.

It's not a Chinese organisation is it?


> One site I can't 'see' is www.linuxtoday.com <http://www.linuxtoday.com> =
 - so you can see the importance of this call for help :-)

This site currently works OK from where I'm sat. Comparing the traceroute I=
 get from here, we both go in to QWest's network (which makes sense ;-) and=
 I also get traceroute strangeness as you indicate. Instead of !A indicated=
 in your dump, I get !X, which indicates that this ICMP service has been ad=
ministratively denied in the QWest network. Therefore, traceroute isn't goi=
ng to help us too much with this problem.

> So two questions:
>
> 1). Can anyone offer an idea of what might be wrong?

I would be strongly inclined to blame it on your ISP's HTTP caches. Especia=
lly if it is only for certain Websites. You may find that they are hashing =
across a number of caches, one of which needs a [reboot|software upgrade|ne=
w disk|bug reporting|whatever]. You may want to check whether they are poli=
cy-routing all TCP port 80 requests through their caches. In this case, eve=
n though you may have proxies disabled, your HTTP requests could still be i=
ntercepted by the caches.

> 2). If it's not me (or something to do with my set up) how can I approach=
 getting it fixed?

I would call the ISP about how their caches are set up and whether there ar=
e known issues with people accessing these sites.
--
rik


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