dns issue?

[Kevin Darcy]

warth33 at hotmail.com wrote:
> Well, I dont know if Im at the right place to post. If not, I hope
> someone can tell me where to post this.
>
> There is a domain, domain.com. And then there is domain2.com. Both
> share the same ip address. Everything seems to work allright.
>
> A couple of times, a fellow tells me that he cannot reach the page. He
> gets a "Page cannot be displayed". I contacted the support for the
> dedicated server. Dont think they solved it. But at some time my
> friend could view the page. Now, something more concrete.
>
> Yestareday, from my computer that is on a router, I viewed the page,
> almost all the day. In the evening, when I typed the url, I got a
> "Page cannot be displayed".
>
> I then opened my laptop (that is not connected to the router, and has
> his own ip address) and browsed to domain1.com. I could see the page
> from there.
>
> I got back to the pther computer, but I could still not see the page.
>
> Late in the evening, after I contacted the support (that only keeps
> saying that they can view the page and that there are no issues on the
> server end) I could visualize the page again. Wow!
>
> Late in the night, again the same problem. NB: at the same time I
> could view the page from my laptop. Actually i always can see the page
> from my laptop.
>
> Today, fro all the day, I have not been able to view tha page. Never.
> NB that domain2.com has almost always been reachable from computer 1.
>
> The support dont seems to care. "It is not a server end problem, we
> cannot do anything about this. The only thing you can do is to contact
> your isp".
>
> So my question is: what happens with all thise people (because there
> are other, Im not the only one. Not many, but I know that there are)
> that will not reach the page? They will type the url, for the first
> time. They will see a page cannot be displayed. And they will never
> come back again.
>
> otherwise, according to the advice I got from the support, I can
> contact my isp and, probably, all the isp in the world and tell them
> that there is/can be some issue with my domain.
>
> is this posible? im not much for sysadmin, but I cannot believe this
> is true. What do you think? Is this a normal situation? I think this
> is unacceptable. Is there anyone that can give me an advice on how to
> try to solve this?
>   
Before you even consider DNS as a possible cause of this problem, you 
should clarify exactly what kind of error your browser is getting. Is it 
a 404 error? That means you talked to the server, but the specific URL 
could not be accessed (e.g. someone deleted the web page). Is it a 403 
error? That's authentication failure, and also indicates that you talked 
to the web server but were not successful in retrieving the URL. Is it a 
5xx-series error? That's a fatal error coming back from the web server. 
All of those errors excuse DNS, since you *did* actually talk to the web 
server, and you wouldn't have been able to do that, presumably, if DNS 
were screwed up.

(Caveats: I'm not a web expert, and the presence of a proxy may 
complicate my descriptions above, since sometimes it will be the proxy 
giving back the error response rather than the remote web server itself).

Depending on your browser, DNS problems may or not be rather easy to 
pick out. In the ancient version of Firefox I use for 
testing/troubleshooting (v1.5), for instance, I get a "Bad Gateway ... 
[code=DNS_HOST_NOT_FOUND]" error if I try to go to a URL with a 
non-existent domain name. Internet Explorer, on the other hand, is 
rather hopeless in this regard, typically sending you off to a "search" 
page if something goes wrong with the DNS lookup, so, even if IE is your 
"main" or "regular" browser, you may want to consider installing some 
other browser if you want to do proper troubleshooting of these kinds of 
problems.

                                                                         
                              - Kevin